What? Where? I didn't see!!

Paula Parungao

They say that the world can only be viewed through our senses. That’s why our senses are so important to us. They let us get a feel of the world that is otherwise unattainable if our senses didn’t exist. What would happen if we can neither see nor hear? Touch nor taste? Smell nor feel? We’d be lifeless. Stuck inside bodies that can never live.

So if our senses is our door to the world and is a means of living, it must be reasonable to imply that we are able to translate everything that we see. After all, it is our way of survival. Haven’t we evolved and continuously adapted for that sole reason? It must make sense then that we are capable of perceiving everything in our world.

Vision is most probably one of the senses we humans are most dependent on. We can judge and describe everything around us just by looking at them. We alter our behavior depending on the things we see. Not only that but the eye is complicated enough as is. It relies on photons and a cascade of molecules to translate light. The inside of the eye itself is made up of complex lenses and light benders that translate what we term as light. When our eyes can properlybend and translate light, we are said to have perfect vision.

But apparently, even with this complicated process, we are more blind than we think. While it is true that we are able to translate everything that we see, we can’t interpret nor perceive everything that, for one, our eyes see for us. This phenomenon is so curious and so unbelievable that it took six researchers to do the study.

Experiment 1

Stimuli (T and L) of different luminance were presented. Participants were then asked to count the stimuli silently. Another trial instructed the participants only to observe the stimuli of certain luminance. Unbeknownst to the participants, a cross of similar or different luminance passes through the screen. After the experiment, the participants were asked to answer a questionnaire asking if they saw anything unusual. It appears that participants more often than not see the unexpected cross when it was the same luminance as the stimuli. Conversely, participants fail to see the unexpected stimuli when it’s the same luminance as the ignored stimuli.

Experiment 2

The next experiment was similar to the first one, only that the background was different. Instead of gray, the researchers decided to use aquamarine. With the same method as the first, it appears that the results reverse. When the unexpected cross was the same luminance, the participants failed to notice while the unexpected cross with a different luminance was seen. According to the paper, an explanation for this was that participants developed a luminance threshold wherein they notice stimuli darker than the threshold while ignoring stimuli lighter than it. It may also be that the unexpected stimuli was more eye-catching. Future study is needed to make a sufficient conclusion.

Experiment 3

We’re back to a gray background but now, the unexpected stimuli is as noticeable as ever. Against a gray background with white and black stimuli, the unexpected cross is now colored red. Surprisingly, when compared to experiment 2, the red cross was actually less noticed.

According to the overall results, it appears that only half of the participants noticed the unexpected object. And about 28% didn’t even notice the blaring and blatant red cross. It seems that when we are involved in certain tasks, we fail to notice other things around us no matter how obvious they may seem to be. This may be why, when we are in a complicated situation, we are asked to take a step back and look at it from a third person’s point of view. In this sense, we are uninvolved and we get to see things clearer.

In terms of perception, no matter how efficient or how special our senses might be, it shows that we don’t perceive all that we see. Even when our eyes may be working at their peak, what matters is still how our brain interprets or perceives all the stimuli it receives. We are inattentively blind to the things around us when we think that they aren’t important. In this sense, Beau Lotto may be right: Context is everything. The context being what matters to us most. What do we want to see?

This study is an eye-opener. It makes one aware of how much we aren’t actually paying attention to. From the looks of it, this may be a physical limitation our brain has created so that our minds wouldn’t be too overridden. Our consciousness already has a lot on its mind (pun intended) not to mention all the information our unconsciousness continuously interprets. When all this stimuli is intentionally perceived, it may cause our brains to implode with too much information. It’s not to say that I’m discouraging people to be more aware of their surroundings. In fact, with this study, I think people should be more aware of this physical limitation so that they can actually make more use of all the information they perceive. Too much information may cause our brains to implode, which is why observation is a conscious effort. The more you exercise this effort, of observing and taking notice more of the things around you, the more you can actually effortlessly see the unexpected things. Therefore, when it becomes innate, you get to maximize all that you perceive and in turn, create a more accurate translation of the world.

To prove that we can all be victims of inattentive blindness, please take the time to watch this video.

References:

Chabris, C.F., Clifford, E., Jimenez, R., Most, S.B., Scholl, B.J., Simons, D.J. (2001). How not to be seen: The contribution of similarity and selective ignoring to sustained inattentional blindness. American Psychological Society, 12(1).

Don't you shiver?: Pleasurable Responses to Music and the Brain

by Isabel Acosta, 2007-49035

(If you love music, I really encourage you to read this seemingly intimidating article!)

Didn’t you just shiver after hearing that song? All its elements –the melody, the tone, the rhythm, the pitch, the singer’s voice, the buildup of instruments –all that abstract jumble of notes and sounds makes my heart soar every time I listen to that song. And apparently, my brain is going crazy as well.

“Music expresses that which cannot be said and on which it is impossible to be silent.” Such powerful words by Victor Hugo, a French poet, novelist and playwright. Music has always been a profound aspect of human life. It affects us in unexplainable and incomparable ways. Those ‘chills’ we feel when we listen to music, those ‘shivers-down-the-spine’ –those occurrences are universally felt and experienced by all of humanity. And two scientists sought to explore and explain the neural mechanisms behind that experience.

Blood and Zatorre (2001) sought to explore what people’s brains looked like while listening to ‘intensely pleasurable music.’ The participants of the study consisted of 10 students from McGill University (five female, and five male) with at least 8 years of music training. Although music training is not needed to experience ‘chills,’ musicians were selected as participants, because the researchers assumed that this group of people would be the exact kind of people to respond emotionally and strongly to music. An important qualifier was that all the participants reported frequent and reproducible experiences of chills. This quality is definitely needed for the experiment to be a success.

After the participants were properly oriented and given consent forms, Positron emission tomography (PET) scans were then performed and registered with Magnetic resonance imaging (MRI) scans. PET is a technique for visualizing brain activity, usually by measuring the accumulation of radioactive 2-deoxyglucose (2-DG) or radioactive water in the various areas of the brain. MRI is a procedure in which high-resolution images of the structures of the living brain are constructed from the measurement of waves that hydrogen atoms emit when they are activated by radio-frequency waves in a magnetic field. So, brain activity was registered with the MRI, so that the researchers can easily locate which part of the brain is activated during listening to intensely pleasurable music. Each participant chose a musical selection which consistently made them experience strong emotional responses (which includes chills). The researchers made the participants choose their own musical selection because music preference varies greatly between individuals, and because this would be the most efficient and direct way to produce the necessary intense emotional responses. All chosen musical selections belonged to the classical genre –there were no words associated with the piece, and they were all of intrinsic value to the participant. The latter assures that the selection does not evoke emotions due to personal associations and/or memories. 90-sec excerpts of the musical piece (which should include the part that specifically gives the person chills) were used as ‘subject-selected music’ for that participant. Each of the excerpts was used as another participant’s emotionally neutral control. This was done to control for confounding variables brought about by varying stimuli. This assures that the analysis of the group-averaged data involves the comparison of identical sets of stimuli (same tempo, same pitch, so no confounding variables --when the data from the subject-selected music condition and the data from the control condition were averaged separately and subtracted from each other during analysis, only the pure emotional valence remained). The participants rated the emotional intensity of their responses to the other nine musical selections of the other participants. A rating of less than or equal to 3 (≤3) out of a 10 was required in order for the selection to qualify as that rater’s control. The participants were then asked to familiarize themselves with their control musical selections in order to control for the confounding effects of novelty.

Each PET scan lasted for about 60 seconds. During these scans, the participant listened passively to one of four stimuli (subject-selected music, control music, and two baseline conditions: amplitude-matched noise and silence). These baseline conditions are needed in order for the researchers to establish the participant’s default state and in order to examine the participant’s full sensory experience. The scan began around 15 seconds after the stimulus was played in order to ensure the stabilization of the participant’s response to the stimulus. Each of the conditions were repeated thrice, and the order of the stimulus representation was pseudorandomized. Heart rate (HR), electromyogram (EMG, a measure of the electrical activity of muscles), respiratory depth (RESP), electrodermal response, and skin temperature were measured during the PET scans using a machine called a F1000 polygraph. After the scans, each participant rated their emotional reactions to each stimulus. Three items were assessed: chills intensity (0 to 10), emotional intensity (0 to 10) and unpleasant vs pleasant (-5 to +5). The pleasantness and unpleasantness scale was needed because the researchers’ previous study was about the brain parts correlated with unpleasant or mildly pleasant emotions elicited by musical dissonance (lacking in harmony of musical notes). The participants were asked to listen to a range of unpleasant musical selections (mildly unpleasant to very unpleasant) and observed the negative/unpleasant emotions evoked by that piece through PET scans. The researchers wish to see if the same neural circuits recruited by the mildly pleasant music/emotion would be recruited by the chills.

The researchers used regression maps to assess the significance of the relationships between chills intensity rating and cerebral blood flow (CBF, as indicated by the PET scans).

In case you fell asleep during this part in your Math class or you simply don’t remember, regression analysis describes an unchanging relationship between two phenomena. The line representing a simple linear regression is expressed through a basic equation: Y = a₀ + a₁ X. X is the independent variable, and Y is the dependent variable (or vice versa). A₀ is the y-intercept (the value of Y when X is zero) and a₁ is the slope of the line. The slope of the line characterizes the relationship between the two variables. Using two more equations, a line can be drawn. The typical distance between the line and all the points (sometimes called the “standard error”) indicates whether the regression analysis has captured a relationship that is strong or weak. The closer a line is to the data points, overall, the stronger the relationship. (Dizikes, 2010)

The researchers performed a number of corrective computations and subtraction analyses in order to control for confounding factors. Within-subject differences in familiarity was accounted for, control music conditions were subtracted from subject-selected music conditions, baseline conditions were subtracted from music conditions to confirm that the CBF decreases/increases in the brain were from the baseline level and not merely differences from the subject-selected and control music conditions. Regression maps were also used to analyze the relationship between psychophysiological activity (HR, EMG, RESP, etcetera) and CBF. Afterwards, regression with chills were recalculated without the effects of these psychophysiological activities.

So what did these researchers find in those scans? They found that the subjects experienced chills during 77% of scans when their selected piece was played. Heart rate, respiratory depth, and electromyogram responses increased significantly during the highest rated chills music condition compared to the control condition. Skin temperature and electrodermal measurements did not differ significantly. No chills were reported during the control condition, and the two baseline conditions. The average rating for chills in the subject-selected music condition was 4.5 out of 10 (responses ranging from 1 to 9). Comparing this to the average rating for emotional intensity (7.4 out of 10) and pleasantness (4.4 out of 5), the researchers suppose that perhaps pleasantness and emotional intensity must reach a certain level before chills can be experienced. I think that this certainly makes a lot of sense. How can one feel that surging chill if pleasantness and emotional intensity are low and weak? The regression analysis correlating CBF and chills intensity ratings point out that:

a) with increasing chills intensity ratings, regional CBF increases (positive correlation) in the:

- Left ventral striatum (VStr)

o role in reward-related behavior, neurons in this region are sensitive to expectation of upcoming reward⁴

- Dorsomedial midbrain (Mb)

o relay station for auditory and visual information, it is also part of a dopaminergic pathway

- Bilateral insula (In)

o integrates sensory and autonomic information from the viscera, damage in this area leads to auditory agnosia or inability to recognize or differentiate between sounds

- Right orbitofrontal cortex (Of)

o receives information from sensory cortices and assigns them a reward value, related to motivational and emotional behavior⁵, and pleasure responses

- Thalamus (Th)

o sensory relay station

- Anterior cingulate cortex (AC)

o autonomic functions, such as regulating blood pressure and heart rate, as well as rational cognitive functions, such as reward anticipation, decision-making, empathy and emotion; role in reward-based decision making

- Supplementary motor area (SMA)

o Involved in planning of motor actions and bimanual control; also in retrieving sequences (and music is thought to be a kind of sequence)

- Bilateral cerebellum (Cb)

o processes input from other areas of the brain, spinal cord and sensory receptors to provide precise timing for coordinated, smooth movements of the skeletal muscular system; also proposed to be involved in some emotional functions such as regulating fear and pleasure responses⁶

b) with increasing chills intensity, regional CBF decreases (negative correlation) in the:

- Right amygdala (Am)

o processing and memory of emotional reactions

- Left hippocampus/amygdala (H/Am)

o functions in consolidation of new memories, emotions, navigation, and spatial orientation

- Ventral medial prefrontal cortex (VMPF)

o involved in processing of risk and fear, and in decision making, deals with emotion regulation

- Bilateral posterior neocortical regions, including occipital, parietal, and temporal cortices (widespread, particularly the cuneus/precuneus regions --region of the medial aspect of the occipital lobe of each cerebral hemisphere). The visual cortex (Vc) is highlighted in the image below.

Pictures a, b and c represent the scans of areas that show rCBF positively correlated with increasing chills intensity, while pictures d, e and f represent the scans of areas that show rCBF negatively correlated with increasing chills intensity.

The researchers also found that increases in psychophysiological activity correlated with increases in rCBF in that thalamus, anterior cingulate cortex, orbitofrontal cortex, insula, cerebellum and supplementary motor area. This basically affirms the relationship of chills and rCBF changes, since changes in autonomic activity and physiology are markers of chills.

What do these all mean? Changing activity was observed in some brain parts associated with the brain’s reward circuitry (left ventral striatum and dorsomedial midbrain, right amygdala, left hippocampus/amygdala and ventromedial prefrontal cortex). Activity was also observed in the paralimbic/emotional regions (bilateral insula, right orbitofrontal cortex) and regions associated with arousal (thalamus and anterior cingulate cortex) and motor processes (supplementary motor area and cerebellum). Apparently, this kind of brain activity is comparable to those observed in people experiencing euphoria, cocaine addiction (Th, In, AC, Am, and VMPF), and eating chocolate. Animal studies confirm that the structures activated in this study (such as VStr, Mb, Am, H, and VMPF) are crucial in the circuitry of reward processes, hedonic (pleasant sensations) impact, reward learning and motivation. Dopaminergic activity is crucial in this kind reward circuitry. Just so that you guys can understand and appreciate these results more, here is a short explanation of how the reward circuit works:

“The natural function of the reward circuit is to provide a reward and associated pleasurable feelings in response to life sustaining functions, such as eating, to encourage repetition of that function. The reward circuit functions through the use of neurotransmitters, mainly dopamine.” When the reward circuit is activated, it triggers a release of dopamine, which induces pleasurable and euphoric feelings or highs in the ventral tegmental area (VTA). Addictive drugs work the same way, they activate the circuit and cause the system to release more than normal levels of dopamine. Some drugs even block dopamine receptors, which are needed in order to control the dopamine available in the synapse. Blocking of receptors results in a build-up of dopamine. Addiction results when the brain gets used to the high levels of dopamine. The user feels the need to keep taking the drug in order to restore ‘normalcy.’ (Quraishi, 2002)

No wonder listening to music is such a rewarding and powerful experience!

The amygdala was of particular interest to the researchers. The amygdala and hippocampus interact with the midbrain in both reward and emotion systems. In cocaine administration studies, decreases in the left amygdala have been correlated with ratings of cravings rather than rush, so the researchers speculate that the decreases of rCBF in the amygdala in this study might be due to the anticipation of the chills rather than the chills response itself. Interesting right? In addition to this, amygdala decreases plus ventral striatum increases indicate that the “approach” and “withdrawal” system might be at work in this study. See, the amygdala is involved in the processing of fear, other aversive emotions and biologically relevant emotions, while the ventral striatum mediates processes associated with reward and motivation/approach behavior. Activity is both structures are also said to be negatively correlated (amygdala activity decreases as a consequence of increased ventral striatum activity) So, relating this to the study, perhaps music is pleasurable because it activates the reward system and because it simultaneously decreases brain activity structures that are associated with negative or aversive emotions. I find this really interesting! Isn’t it astounding how physiology explains and makes sense of something as abstract as music? Our brain really is such a beautiful aspect of humanity.

Lastly (phew, I know right, they found a lot of things in this study), remember that the researchers wanted to integrate this study with their previous study of music unpleasantness and pleasantness? Well, the researchers found that brain structures associated with intensely pleasant emotion elicited by music were different from the brains structures associated with unpleasant responses to musical dissonance (right parahippocampus, if you were curious). This is important because it suggests that negative emotions are specifically-related to this brain region. Structures that are involved in reward/motivation processing were not related to the structures activated by pleasant responses to musical consonance (harmonious songs), except for the ventromedial prefrontal cortex and the orbitofrontal cortex. This suggests that these brain parts probably respond to multiple emotions.

It's pretty obvious that I am really, really interested in this topic, and that the study really drew me in. I was really impressed with how the study was planned and conducted. The researchers really controlled for every possible confound, and such foresight is not present in a lot of researches. They handled such an abstract concept so intellectually and so efficiently, that it is no wonder why this study has been cited numerous times. I was really drawn into the essence of the study. I was really amazed at how physiology makes sense of an immense feeling I thought was too abstract and too grand to be explained. It is really astounding how physiology makes sense of music, and at the same time, the study of music sheds some light on the workings of the very complex human brain. There is logic and meaning in all life occurrences! The dynamics of it all makes me appreciate even deeper music and the beautiful plan or blueprint of the human body. I also think that is just interesting that listening to music evokes the same response as biologically relevant stimuli. Unlike eating and sexual intercourse, music has no adaptive or reproductive function, yet it activates and recruits the same neural systems of emotion and reward. The reward circuitry, in particular, exists to reinforce the repetition of actions that ensure our survival and self-preservation. Why then is there a need for constant and consistent music exposure? I do not know, but the researchers propose that appreciation of music may just be an emergent property of the complexity of human cognition. Perhaps as our primitive brain systems started to evolve into more complicated structures, human beings gained the capacity to assign meanings to abstract stimuli and derive pleasure from them. Whatever the reason is, this study only proves that music, despite lacking in survival and life-sustaining significance, is probably significant to our psychological well-being. Music must be contributory in this sense for it to affect our brain systems so immensely. I am sure that most of us, if not all of us, can agree that music affects us and benefits us in much deeper ways than even our most primary needs. Indeed, Nietzsche was right, “without music, life would be a mistake.”

Didn’t that article just make you shiver? Here’s another song to shake up your brain. Ooh and aah, feel your brain slowly lighting up. Enjoy that glorious pleasure, it’s good for you ;)

Sources:

1) Blood, A. J., & Zatorre, R. J. (2001). Intensely pleasurable responses to music correlate with activity in brain regions implicated in reward and emotion. (M. E. Raichle, Ed.) Proceedings of the National Academy of Sciences , 98 (20), 11818-11823.

2) Dizikes, P. (2010, March 16). Explained: Regression analysis. Retrieved July 29, 2010, from MIT News: http://web.mit.edu/newsoffice/2010/explained-reg-analysis-0316.html

3) Pinel, J. P. (2008). Biopsychology (7th Edition ed.). Jurong, Singapore: Pearson Education South Asia Pte. Ltd.

4) Ventral striatum plays important role in circuitry of reward-oriented behavior: Researchers. (2010, May 5). Retrieved July 29, 2010, from The Medical News : http://www.news-medical.net/news/20100505/Ventral-striatum-plays-important-role-in-circuitry-of-reward-oriented-behavior-Researchers.aspx

5) Cerebellum. (2010, July 15). Retrieved July 29, 2010, from Wikipedia: http://en.wikipedia.org/wiki/Cerebellum

6) Rolls, E. T. (2004). The Functions of the Orbitofrontal Cortex. Brain and Cognition , 55 (1), 11-29.

7) Quraishi, S. (2002, January 2). Addiction and Reward Circuit. Retrieved July 29, 2010, from Serendip: http://serendip.brynmawr.edu/bb/neuro/neuro01/web2/Quaraishi.html

8) Wikipedia.com

Quitting smoking is easy. I've done it a thousand times.

by Cristina Menchaca (2007-49018)

Smoking is one of those things people tell you not to get into because once you're in, it's hard to get out. And well, it's bad for your health. Smoking has been a huge public health problem all over the world, and it leads to many deaths- even if you're not the smoker (secondhand smoke). Everyone knows that smoking has negative consequences. We can all say it along with the advertisers: 'government warning, cigarette smoking is dangerous to your health'. Yet of the very few smokers who try to quit on their own, they can abstain only for so long. Why is it so hard to remain nicotine-free? There are two main factors for failing to abstain from smoking: one, people go back to smoking to relieve the withdrawal symptoms they experience from not having nicotine anymore, and two, people go back to smoking after they're exposed to smoking-related cues, which of course, elicit craving responses. This quote might looks at how strong the craving is: I read that smoking is bad for your health. This upset me so much that I decided never to read again.

One year ago, a group of researchers looked at how the brain looked when people abstaining from smoking saw pictures related to smoking. What did they find out? Something that goes like this: whenever I think about quitting smoking, I need a cigarette to think. In other words, the brain's reactivity to smoking-related cues could be a reason why it's hard to quit smoking, and, reactivity in the brain could change depending on how long it has been since a person has stopped smoking.

The technique used to look at brain reactivity in response to the stimuli was the fMRI (ferro-magnetic resonance imaging). Two types of stimuli were shown to the participants: either smoking-related images (people smoking, hands holding cigarettes, or just cigarettes) or neutral images (faces, hands, as long as they had no cues for smoking). The participants in the study were not just any kind of smoker but were smokers classified as nicotine-dependent, and this was based on the DSM-IV (Diagnostic and Statistical Manual of Mental Disorders). There were 13 participants, all of whom were females (with a mean age of 43) and who happened to be taking part in a clinical trial on smoking cessation. Their consent and the consent of the hospital was taken, of course. Brain reactivity to the stimuli were measured twice: once before the attempt to stop smoking (prequit), and the second time after extended smoking abstinence (about 52 days). During the cessation period, participants were aided by nicotine replacement therapy, or NRT, to help them in their abstinence from smoking. Amount of NRT administered was also reduced in time.

The stimuli were shown to the participants as colored pictures. Aside from the smoking-related and neutral pictures, target images of animals were also used to ensure that participants were paying attention in the study (participants had to press a button upon seeing the picture of an animal). A total of 42 smoking, 40 neutral, and 8 target pictures were shown to each participant in a pseudo-random order. Each picture was shown for 4 seconds, and there was a break of 14 seconds between pictures. To avoid practice effect, different pictures were used the second time of testing (extended smoking abstinence of about 52 days). Not only were the reactivities between neutral stimuli and smoking-related stimuli used, but a within-subjects design was also used to compare reactivities before and during extended smoking abstinence.

It was found that there was more brain activity for cigarette-related stimuli than neutral stimuli. It was also found that during the period of extended smoking abstinence, reactivity of the brain was in specific areas of the precaudate nucleus, the prefrontal, primary somatosensory, temporal, parietal, anterior cingulate, and posterior cingulate cortexes. Too much neuro terms? Basically, the mentioned areas are those that have to do with attention, somatosensory processing, motor planning, and conditioned cue responding. The regions involved in the fMRI scans were those that have to do with reward, craving, emotional processing, memory, visual attention, and impulsivity. The fact that the previously mentioned parts of the brain show more activity after a long period of cessation (about 52 days) means that even after such time, reactivity to smoking-related stimuli still persists. Not only does reactivity persist, but in some parts of the brain, reactivity was shown to be even more intense during the extended cessation period. The caudate nucleus and other areas involved in learning, action planning, and motor behavior, are examples. This could probably be the reason on why people are vulnerable to persistent relapse even if it has been days since one's last cigarette. The insula, which has do do with maintenance of behaviors, craving, and exposure to cues, was also active during both scans (prequit and extended abstinence).

For more specific ares of the brain and what they correspond to, read this (if not, skip to the next paragraph!):

The first and second fMRI results (prequit and extended smoking abstinence) showed that there was a significantly greater activity in the brain for smoking-related images than for neutral ones. Areas of the brain that showed activity in both scans were the frontal, anterior cingulate, posterior cingulate, temporal, parietal, and occipital areas. Across time, the different areas of the brain that showed activity were the frontal, anterior cingulate, posterior cingulate, temporal, and parietal areas (cortically) and the cortical nucleus (subcortically). Such regions have been shown to be active with smoking-related and and drug-related cues. The first scan revealed an increase in regions involved in emotional processing (frontal and anterior cingulate cortexes), visiospatial processing areas, and temporal areas correlated to smoking cues. The second scan showed activity in the prefrontal, anterior cingulate, posterior cingulate, temporal, and parietal areas, and the caudate nucleus. Such areas have to do with action planning, habit learning, and craving. Specifically, the anterior cingulate cortex is an area that deals with cue-induced motor responses, the posterior cingulate cortex is an area that gives attention to reward-associated stimuli, and the prefrontal, parietal, and somatosensory cortexes are involved in imagined and executed movement, which can promote the reinitiating of smoking.

I'm honestly very impressed with this study and I'm not saying that just because I'm writing about it. I liked that the researchers thought about almost every single detail in their study to make sure that they get results as accurate as they can. They chose participants who all wanted to stop smoking, and they did not include women with an unstable mental illness, a lifetime diagnosis of an organic mental disorder (schizophrenic, bipolar, etc.), a history of alcohol abuse, and women who were unresponsive to an adequate course of NRT, depressed (the Hamilton Rating Scale for Depression, administered again after the first scan), or pregnant (urine test). Vital signs were also checked for normality, and even recent smoking and alcohol use were tested, especially before scans. Also, aside from using the DSM-IV to get nicotine-dependent participants, another test was used (the Fagerstrom test for nicotine dependence). Even hormone levels were taken into consideration: the second scans were taken at around the same point in the participant's menstrual cycle for the first scan. I also liked that NRT was very individualistic so that abstinence could be maximized: each participant was given a specific dose depending on her highest and lowest tolerable doses that effectively blunt withdrawal symptoms. I liked that the use of target images were to ensure that the participants were taking the study seriously, and that the use of neutral images was to ensure that change of brain activity was not an effect of time (or the state of smoking) only. And as a whole, I liked that this study was a spin-off of a previous study that examined fMRI activity but only after 24 hours of cessation. The results were the same as this study (showing support for the incentive-sensitization theory, where the perceived reward value of a drug-associated cue increases during abstinence). It is important to look at brain activity more than 24 hours after cessation if one wants to know whether enhanced reactivity contributes to relapse, which occurs after one has abstained after quite some time. I also liked that the researchers had a defense as to why they had no placebo (in place of NRT), and that it is because the increased brain activity could not have been a result of NRT. If it was, it would have shown clinically, based on NRT users. They also explained that although they did not get participants' subjective ratings on cravings, suggestions are that such answers will minimally inform fMRI data anyway. Very well-thought out indeed!

How does this study...

relate to my current topic in the course of perception? Well, we've been talking about the physiology of perception. Although this study did not mention steps from a stimulus to the brain and from the brain outwards, we know that the stimuli used (neutral images and cigarette-related images) are attendedto by sensory receptors (our eyes), and the sensation is transduced through neural communications into electrical energy. The message is sent to the brain, which in this study, are the different parts that react to the stimuli, that in turn, helps us experience the stimulus, give it meaning, and act on it. From the various parts of the brain, messages are sent to different parts of the body. This is what makes quitting smoking hard. The parts of the brain that are 'activated' are those that have to do with craving, impulsivity, reward, etc. The fact that the different parts of the brain and different parts of the body are stimulated means that the stimulus was strong enough for action potential to occur and send the messages from neuron to neuron, from the optic nerve, to various parts of the brain, to various parts of the body. This whole study shows how the perception of a visual stimulus, such as pictures, causes abstaining smokers to be more likely to relapse. It's because of the signals being sent from neuron to neuron, first hitting the eyes, then getting passed on to the brain, then from there, to different parts of the body as a result of the brainareas that were activated.

So after praising the study, how else could it be improved? One way would be to increase the sample size. Although it's good that the participants were carefully chosen, the researchers were left with 13 participants, not a big enough number to make firm establishments and generalize results. At the same time, participants were all females, and the researchers themselves said that men should also be considered, to see if sex has different implications. It would also be recommendable to make use of participants who are from different areas of the world (or of different cultures), if, as in the case of sex, culture would have different implications. According to the study, brain reactivity to such stimuli for people during smoking is not known, neither after extended periods using NRT (longer than the time in this particular study). Having such information would be good so that parts of the brain involved in relapse vulnerability can be known, and perhaps from such data, medicines for abstinence could be made. Additionally, NRT is known to be only effective for short-term withdrawal symptoms, which suggests that reactivity persists and results in craving or relapse. An extended scan to the point of very reduced (or even none of) NRT would be highly useful in figuring out the physiology behind cravings or relapse during abstinence. Finally, it might be interesting to make use of actual stimuli, not just pictures. If the stimuli used were only images and they already created such activity in the brain, what more real and tangible stimuli? It is no wonder then that people addicted to smoking have a hard time stopping. In fact, some of the participants had slips (smoking part of a cigarette once during the period of cessation), yet they were not excluded from the data because slipping is considered part of going through the NRT experience. And if researchers are interested, they may want to look into how depression comes into the picture. After the second scan, participants showed a higher level of depression, even if they were still in the normal range. Was this a withdrawal symptom? Was it because the body could not satisfy the crave its brain was acknowledging?

So many questions that spring from this study, but it still gave answers on what really is happening behind the scenes, physiologically speaking. What's my moral of the story? Well I'm not going to be naive and tell people not to smoke, because it's really not in my hands. Practically speaking, I'd say to make sure you don't get into the habit of it, or else sooner or later, you'll have the hardest time quitting. The brain can attest to that. And if you do get to that point, you'll probably end up saying, 'I'd stop smoking but nobody likes a quitter'.

Source:

James, A., Frederick, B., Merlo-Pich, E., Renshaw, P., Evins, A. E., Fava, M., et al. (2009). Brain fMRI Reactivity to Smoking-Related Images Before and During Extended Smoking Abstinence.Experimental and Clinical Psychopharmacology, 17(6), 365-373.

WOW, 3-D! :D

by Michelle T. de los Santos



"Whoaaa! Inception and Despicable Me in 3-D, the best! Awesome okay! :))" -Mitch

We live in a three-dimensional world, but our eyes only receive two-dimensional images. We then thought of the question "How does our brain combine these images into a 3D percept?". We can't deny that most of us have a great appreciation for 3-D structure of scenes, that's why we like, love, and prefer to watch movies in IMAX 3-D right?! That's why nowadays technologies are continuously evolving. They even created 3-D TV's for better appreciation of scenes. Since our current topic in my Psych 135 course, sensation and perception, is about physiology of perception, I was inspired to look at the neurological or physiological structure of this 3D - visual experience -- the physiology of depth perception.

The three-dimensional (3-D) structures that we see have something to do with our judgment of depth. Certainly, our eyes are so incredible that they enable us to see wonderful things in life. Researchers explained that humans could make precise judgment of depth because of motion parallax. Motion parallax is the relative retinal image motion between objects at different distances, that is whether an object is near or far relative to the plane of fixation. See figure below. However, motion parallax alone is not enough to specify the sign of depth, rather the direction of image motion relative to observer motion is important (Nadler, Angelaki, and DeAngelis, 2008).

Our judgments of depth can be referred as depth perception. I agree when the researchers mentioned that perception of depth is a fundamental challenge for the visual system, particularly for observers moving through their environment. I learned in the journal that in order to reconstruct the three-dimensional structure of a scene (3-D), the brain makes use of multiple visual cues. As I mentioned above, one potent cue that they studied was motion parallax, which frequently arises during translation of the observer because the images of objects at different distances move across the retina with different velocities. Under some conditions, the researchers explained that the brain could interpret such ambiguous visual motion by using other cues such as occlusion, size or perspective. Human psychophysical studies have demonstrated that motion parallax can certainly be a powerful depth cue, and as they mentioned, motion parallax seems to be heavily exploited by animal species that lack highly developed binocular vision.

The researchers recorded extracellular single-unit activity from middle temporal area (area MT), the visual area of the brain, by using tungsten microelectrodes (FHC) in two adult rhesus monkeys (Macaca mulatta). The following are the summarized method of the researchers: A custom-made virtual-reality system was used to provide stimuli consisting of sinusoidal translation and/or visual motion. In addition, it displays that simulated objects at different depths, that many neurons in the middle temporal area (area MT) signal the sign of depth (near versus far) from motion parallax in the absence of other depth cues. Animals were trained to maintain fixation on a visual target during translation of the motion platform. Custom-written OpenGL software was used to generate visual stimuli that depicted a random-dot surface at one of several possible depths in a virtual environment. The visual stimulus was viewed monocularly by the animal, and all pictorial depth cues were removed from the stimulus to render the visual motion ambiguous with respect to depth sign. Thus, to compute depth sign based on motion parallax, neurons needed to combine visual motion with extraretinal signals generated by physical translation of the animal (for example, vestibular or eye movement signals).

The experimental design of Nadler, Angelaki, and DeAngelis (2008) compared neural responses in two conditions. 1 – A Motion Parallax (MP) condition in which the combination of physical translation and visual motion specified depth unambiguously. 2 – Retinal Motion (RM) control condition in which the same visual motion stimulus was presented in the absence of extra-retinal signals, thus rendering it ambiguous with respect to depth sign. Neuronal responses were measured as mean firing rates, and the significance of depth-sign selectivity was assessed with permutation tests. Eye position data were filtered (200 Hz lowpass) and analysed to quantify the accuracy of pursuit eye movements.

After reading their method, I felt like whoaaa! Well, I was amazed by their procedures because it seems complicated but they were able to do it as organized and detailed as possible that’s why I like their method. They were able to show the physiology of perception, from stimulus to the brain, and how will the brain process the stimuli/signals. Although, not all can understand their experimental design but no worries that’s expected. In addition, all their procedures were approved by the Institutional Animal Care and Use Committee at Washington University and were in accordance with National Institutes of Health guidelines. Hence, their experimental design will not be in trouble, I hope!:)

The findings of the study come up with the mechanism that generates depth-sign selectivity in area MT. The researchers mentioned that it might possibility be an extra-retinal signal related to head or eye movement simply sums with responses to visual motion, thus enhancing responses to one depth sign (for example, near) and suppressing responses to the opposite depth sign. The data of their study suggest that the mechanism is more complicated, as they have shown that single neurons in area MT carry reliable information about depth sign from motion parallax. Therefore, their findings provide evidence for a neural substrate for this perceptual capacity. Although they mentioned that they cannot yet prove that these signals in area MT are used by the monkey to perceive depth (they might reflect extra-retinal signals used for another purpose), but their findings enable a direct causal test in trained animals. “Such proof notwithstanding, results of the study establish a new potential neural mechanism for processing depth information and suggest that area MT may be involved in integrating multiple cues to depth.” - Nadler, Angelaki, and DeAngelis (2008)

To improve this study, one way is to increase the sample size because they only use two participants, which is not enough to make reliable results. Humans are also better participants so that the study can be more satisfying, although using humans in such experimental design needs considerations. Researchers can also use neuron-imaging (fMRI) to understand the mechanisms underlying visual motion and depth perception better. Researches also need to prove the signals in area MT used in the study if it's really the one used to perceive depth.

Indeed, the study requires to have at least basic knowledge about physiology of perception to somewhat recognize and understand some terms and concepts in the journal. Even I, a Psychology major, cannot understand some of the words and concept in the journal, well, honestly, for me the article was a bit hard to digest and it's complicated. Basically, I just showed a neural representation of depth from motion parallax in middle temporal area or the visual cortex of the brain; the neural circuits underlying the perception of 3D motion. Depth perception are certainly the best! With that, I just want everyone to appreciate and understand how magnificent our brains are and how our brain combine images into a 3-D percept, that enable us to see and enjoy our three-dimensional world to the fullest. Here, see it for yourself! :)

Reference:
Nadler, J.W., Angelaki, D.E., and DeAngelis, G.C. (2008). A neural representation of depth from motion parallax in macaque visual cortex. Nature 452(7187), 642-645.