Biology 202

             In order to be diagnosed with anorexia nervosa, a person must meet the DSM-IV criteria for the disorder. This includes a body weight less than 85% of that expected, a preoccupation with food or feelings of becoming fat, a disturbance in self-image, and the absence of a menstrual cycle in females.  An estimated .5-3.7% of females will meet these criteria—will suffer from anorexia nervosa—in their lifetime (6). Though these prevalence numbers are not as high as many other disorders, anorexia nervosa (AN) remains a serious concern; it has one of the highest mortality rates of any psychiatric disorder (5). But what causes AN? Many studies, and much media attention, have focused on environmental and cultural factors that play a role in the development of AN. But in addition to these factors, newer research suggests that there is also a biological basis that makes certain individuals more vulnerable to the disorder.

Imagine a world in which you had a song playing non-stop in your head and there was no way to stop it. Your brain was constantly in listening mode and the music in your head was always on full volume. This is what it would be like to suffer from music hallucinations. It is normal to hear an occasional song in your head, but generally it eventually goes away because the brain is bombarded with numerous other signals and stimuli that we are able to focus on instead. Music hallucinations occur when a set of neurons in the brain begin to misfire and patients feel as though they are always hearing music, even though in reality there is nothing playing. There is no other symptom of music hallucination and studies have shown that music hallucination tends to be the only psychosis problem in patients, the main concern being that these hallucinations are very annoying.

It’s unlikely that pheromones will ever be used in a pick-up line; however, scientific research has shown that pheromones could play a part in human sexual attraction.  Since the 1980s, when pheromones were discovered to exist in humans, numerous perfume companies have launched marketing ploys to sell people “magic” scents to improve their sex lives.  There is much debate about the potency of pheromones in human relationships, but pheromone research has lead scientists to question our independence in mate selection.  It has also spurred questions about the difference between consciousness and unconsciousness.  How much can we actually control?  That is the question.

A recent study found that the Alzheimer’s disease rate in Asian Indians is only 25% of the rate in the developed world.  While more than 10%  of Americans over the age of sixty five suffer from Alzheimer’s Disease, only 1% of their North Indian peers suffer from the same disease (1).  This finding prompted researchers to dig deeper into understanding why such a disparity exists between the two nations.  Understanding the disproportion of incidents is not a simple task, for the underlying causes and mechanisms of Alzheimer’s disease are not fully understood.

Modern life in the twenty-first century might be defined by the state of sensory overload.  Cell phones and iPods, Blackberrys and computer screens, fast food and designer perfume put our ears, eyes, nose, tongue and skin into overdrive.  What saves us from falling into a tangled web of sensory data might lie in our ability to classify these sensations into distinct categories.  In other words, I might be listening to Fergie while eating a peach while watching Entourage while scratching my leg, but I am comforted by the cognitive awareness that each sensation, although simultaneous, is separate.  Then what of the synesthete, those rare individuals who experience the neurological phenomenon of two or more sensory perceptions from a single stimulus <a href="/exchange/#1">(1)</a>?  Is their condition of synesthesia a burden or an inspiration in this world of overwhelming sensory stimulation? 

    Scientists first documented synesthesia in the 1880’s, when Francis Galton observed that certain otherwise physically normal people experienced specific colors upon hearing specific sounds or seeing specific numbers <a href="/exchange/#2">(2)</a>. Interest in synesthesia then waned as research in psychology focused on behavior rather than cognition, but synesthesia has recently reemerged as both a legitimate and exciting topic of research linking neuroscience, psychology and genetics <a href="/exchange/#3">(3)</a>.  A pioneer in the modern study of synesthesia is Richard  Cytowic, whose research in the 1980’s proposed that synesthetes experience this condition involuntarily, project the experience beyond “the mind’s eye”, maintain their intersensory experiences consistently throughout their lives and are more common in women and non-righthanded individuals <a href="/exchange/#1">(1)</a>.  Cytowic links the cause of synesthesia to a decrease in blood flow and oxygen delivery within the left hemisphere of the neocortex <a href="/exchange/#1">(1)</a>. Also during the 1980’s, Simon Baron-Cohen and his colleagues at Cambridge University proposed that Neonatal Synesthesia (NS), a condition in which humans up to four months in age experience sensory input without differentiating the source of stimulation, is a normal phase of human development.  According to Baron-Cohen, adult synesthesia results from neurological abnormalities that do not reduce the sensory connections of the neonate stage <a href="/exchange/#4">(4)</a>. Indeed, this neurological “abnormality” is estimated to occur in 1 out of 200 people and can manifest in over 100 different types of synesthesia.  Nevertheless, synesthesia is typically an additive sensory condition experienced in one direction: while a synesthete might always perceive the number seven as yellow, the color yellow will not trigger the perception of the number seven <a href="/exchange/#5">(5)</a>.

Among the most exciting recent research on synesthesia have been conducted by Vilayanur Ramachandran and Edward Hubbard of the Center for Brain and Cognition at the University of California at San Diego, who have contributed new neurological evidence to explain the synesthetic experience.  Their research provides further insights into the evolution of thought, language, and human consciousness, and their approach sheds light on the neurological process of cross-modal perception in separate areas of the brain <a href="/exchange/#3">(3)</a>.  They have explored two possible causes: 1) the tendency of bordering brain regions to inhibit mutual activity: when a chemical imbalance blocks the inhibitory neurotransmitter or fails to produce an inhibitor, cross-linking occurs; 2) a genetic component mutates connections between typically segregated brain areas <a href="/exchange/#3">(3)</a>.

 Ramachandran and Hubbard have used the technology of Functional Magnetic Resonance Imaging (FMRI) to compare the brain activity of synesthetes with those of normal perception.  Their lab has traced neural signals traveling by optic radiation from the retina to the area of the brain labeled “17”, an area in the occipital lobe linked to the perception of color, form, motion, and depth.  From “17”, the neural signals travel to an area labeled “V4”, which they propose is the site for cross-linking between color and numbers.  They demonstrate that this “V4” area was highly active in synesthete subjects that perceived white colored numbers against gray backgrounds, while remaining inactive in subjects with normal perception.  They hypothesize that the perception of colors travel to a “higher” area near the junction of the temporal, parietal and occipital (TPO) lobes that is similar to the neurological site of numerical computation <a href="/exchange/#3">(3)</a>.  However, Ramachandran and Hubbard also argue that there are synesthetic subjects that associate certain colors with the visual appearance of the number rather than with the mathematical concept of that number.  That is, these synesthetic subjects did not perceive colors when Roman numeral equivalents were substituted for Arabic numerals that typically triggered colors.  These findings suggest that grapheme-color synesthesia occurs within the fusiform gyrus that is involved with analyzing visual forms rather than abstract concepts.  Yet for synesthetes, in which the abstract concept of numbers triggers colors, the cross-linking occurs between the angular gyrus near the TPO lobes. 

This brief summary of recent research on synesthesia demonstrates that our knowledge of this condition is constantly expanding, and the only safe conclusion that can be made at this time is that gene mutation causes the ever-expanding variations of synesthetic experience.  However, the connection between synesthesia and genetics raise several important questions for future research.  Which gene is linked to synesthesia?  Can synesthesia be cultivated?  And can synesthesia shed light on the profound questions of human experience related to consciousness, language and abstraction?  “Given the right questions, the right experiments and the right patients, the study of synesthesia might illuminate the very questions that have remained in the domain of philosophers” <a href="/exchange/#6">(6)</a>.

Web Resources

1. <a name="1"> )</a><a href=" http://psyche.csse.monash.edu.au/v2/psyche-2-10-cytowic.html ">; </a>; Synesthesia: Phenomenology and Neuropsychology, A Review of Current Knowledge</a>

2. <a name="2"> )</a><a href=" http://www.bbc.co.uk/radio4/reith2003/lecture4.shtml ">; </a>; BBC Reith Lectures 2003, The Emerging Mind</a>

3. <a name="3"> )</a><a href=" http://psy.ucsd.edu/chip/pdf/SciAm_2003.pdf ">; </a>; Scientific American, May 2003</a>

4. <a name="4"> )</a><a href=" http://psyche.csse.monash.edu.au/v2/psyche-2-10-cytowic.html ">; </a>

5. <a name="5"> )</a><a href=" http://psyche.csse.monash.edu.au/v2/psyche-2-27-baron_cohen.html ">; </a>; Is There a Normal Phase of Development, Departments of Experimental Psychology and Psychiatry at The University of Cambridge</a>

6. <a name="6"> )</a><a href=" http://www.neurologyreviews.com/jul02/nr_jul02_mindseye.html ">; </a>;; The Neurology Reviews</a>

            The Bryn Mawr community proudly and vocally offers an open and accepting space for all walks of gender and sexuality, offering its students an opportunity for personal exploration and growth, both as participants in and/or supporters of the queer community.  Simply living on this campus is an experiment in the complexity of gender and sexual identities, and the variation from individual to individual.  Even general terms defined today, such as lesbian, gay, bi, or heterosexual are not inclusive enough to adequately “label” all forms of sexual orientation (not surprisingly many people would prefer not to be labeled), and gender identities serve as an even greater example of complexity.  One identity in particular, that of transgendered individuals, specifically transsexuals, poses a particularly intricate mix of gender and sex “norms,” prompting questions about both the mental and physical aspects of the self in creating identity.

It happens to all of us occasionally. As you walk down the hallway you see a familiar face—someone you have recently met—you reach into your brain expecting a complicated series of synaptic firing to bring forth the name person in front of you only to be disappointed. Although you know it is there in the recesses of your mind, you cannot summon the name of your new acquaintance. You settle instead for the ubiquitous nod and the word “hello”.

Where failure to occasionally recall the name of new acquaintance may feel uncomfortable, it typically does not create huge difficulties. For me this scenario happens all too often. Names of acquaintances and friends of less than a year’s duration frequently elude me at pivotal movements. Although my problem with name recall is worse for personal names, I also occasionally experience difficulties recalling the name of specific objects or “common names”. Indeed my friends and colleagues are familiar with me using the most round-about ways to identify specific people or objects. Physicians and psychologists have several clinical terms to describe this word-finding problem. Anomia is one general term for problems with word finding or recall that occurs with no impairment of comprehension or the capacity to repeat the words; the terms anomic and nominal aphasia are also used. (1)

Sleeping is something everyone does each day without consciously thinking about why it is so important. We know we are tired before we sleep and if we don’t sleep, but have we ever stopped to think about what our dreams do? Dreams are part of every night’s sleep whether we remember them or not. They are an integral part of our daily rest cycle.

There are five main stages of sleep. Stage I only lasts a few minutes and is characterized by the individual being somewhat awake and aware, but very relaxed. Stages II and III are deeper levels of sleep but the individual will still wake easily. Stages II and III only last for about 40 minutes before Stage IV sleep begins. Stage IV sleep is difficult to wake someone from and is characterized by decreased blood pressure, heart rate, movement and breathing. This type of sleep helps the body recover physically from the day. Stage IV sleep becomes longer if one engages in a lot of strenuous activity and is usually the type of sleep recalled in the morning. After Stage IV sleep is achieved for about 50 minutes, the individual starts to move back down through the levels of sleep back to Stage I. REM (rapid eye movement) sleep begins at this time and is distinguished by “frequent bursts of rapid eye movements…autonomic activity, muscular twitching, dreams and profound muscular relaxation” (2). Both genders experience irregular heart rate and irregular blood pressure as well as increased gastric secretions during REM sleep, while males also experience erections. The cycles of sleep do not last for the same amount of time all night; “Everyone goes through an average of four or five cycles of sleep each night, each lasting from 90 to 100 minutes. Stage IV decreases and REM sleep increases progressively with each cycle, so that most Stage IV sleep occurs early in the night and most REM sleep during the last few hours before arising” (2).

Aditya Vora                                                                                                                                     Neurobiology and Behavior 2007

Paper 2                                                                                                                                                                       April 10, 2007 

Personality is arguably one of humankind’s most complex and fascinating features. Unfortunately for academia, centuries of philosophical musings and psychological studies have shown that personality is also one of the hardest aspects of human nature to conceptualize, exacerbated by the fact that it is also difficult to give it a definition that everyone can agree upon. Putting disagreements aside for the purpose of the discussion at hand, in this essay term “personality” will be defined as an individual’s sense of self, and from this how that individual then interacts with his or her cultural environment. Knowing that every one of 6.5 billion human beings on the planet is in possession of this incredibly intricate feature, a question that may follow is “From where, exactly, does personality arise?” While some argue that personality is a result of genes inherited from an individual’s parents, others claim that it arises simply from the way one is raised. This age-old “nature versus nurture” argument has plagued behavioral scientists and parents throughout the ages. However, perhaps some clarity can be gained on this issue by taking a step back and looking at the even broader picture, that is, what is the mechanism that gave rise to personality in the first place? If personality is taken to be a function of the brain it can then be said that, at least from the perspective of a neurobiologist, personality is a biological aspect displayed by an organ of the body. This said, one may ask, “By what mechanism do all other biological processes arise?” Thanks to Darwin and other contributing scientists, we know the answer to this question is, of course, evolution by natural selection. Thus it must be that human personality, just like any other part or function of the human body, was formed and shaped and is continually formed and shaped by the process of natural selection.