Posts Tagged ‘Perception’


Learning to read emotions and faces is important for our well-being.  For some of us, the act of gazing into another person’s eyes is innately rewarding … especially if they are smiling.  New mothers and their infants can be found locked in each others smiling countenance … thus strengthening the developing neural pathways upon which the infant’s future social skills will grow.

One component of these neural pathways is the CNR1 gene expressed in the striatum and other brain regions that process rewarding and positively-reinforcing stimuli.  For most of us, a happy smiling face is positively rewarding … moreso with certain CNR1 genotypes.

From Drs. Baron-Cohen and Chakrabarti:

“A comparison of these results with those from our earlier fMRI study reveals that for the SNP rs806377, the allelic group (CC) associated with the highest striatal response is also associated with the longest gaze duration for happy faces. For rs806380, the allelic group associated with the highest striatal response (GG) is also associated with the longest gaze duration for happy faces.”

My 23andMe profile shows both the long-gaze CC and GG genotypes for rs806377 and rs806380.  Mmmmkay … I guess this would be a good time to apologize to all the girls I inappropriately stared at in the cafeteria back in college … even though you weren’t usually smiling back at me.  I guess my CNR1 and striatum were pretty overactive.

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Kim Kardashian
Image by BiggerPictureImages.com via Flickr

Sometimes, when flipping channels late at night, its hard NOT to stop and gawk at the various spectacles on reality-trash-TV.  No self-respecting scientist would admit to being smitten by all the vanity and preening – right?  Well, back in 2002, there was a mouse whose homeobox-B8 gene was disrupted – who caused a minor media sensation in the community – for its tendency toward, “excessive grooming … not unlike that of humans suffering from the OC-spectrum disorder”.  Hunh?  A mouse not-unlike trash-TV celebs who can’t stop fixing their hair?  An interesting genetic effect to be sure.

A recent paper, “Loss of Hoxb8 alters spinal dorsal laminae and sensory responses in mice” reports a closer look at this mouse mutation and provides evidence that the excessive grooming is, instead, a consequence merely of “itch perception” which arises from disrupted development of itch specific GrpR-positive neurons in lamina I of the dorsal spinal cord“.  Indeed, when the investigators applied sub cutaneous lidocaine to the peripheral nerve endings in the groomed regions – the excessive grooming stopped.  If you are interested in the development of the peripheral nervous system, the paper is well worth a read!  If you are into the psychology of excessive grooming, the Kardashian sisters always provide a steady stream of data.

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This year, my 5 year-old son and I have passed many afternoons sitting on the living room rug learning to read.  While he ever so gradually learns to decode words, eg. “C-A-T”  sound by sound, letter by letter – I can’t help but marvel at the human brain and wonder what is going on inside.  In case you have forgotten, learning to read is hard – damn hard.  The act of linking sounds with letters and grouping letters into words and then words into meanings requires a lot of effort from the child  (and the parent to keep discomfort-averse child in one place). Recently, I asked him if he could spell words in pairs such as “MOB & MOD”, “CAD & CAB”, “REB & RED” etc., and, as he slowly sounded out each sound/letter, he informed me that “they are the same daddy“.  Hence, I realized that he was having trouble – not with the sound to letter correspondence, or the grouping of the letters, or the meaning, or handwriting – but rather – just hearing and discriminating the -B vs. -D sounds at the end of the word pairs.  Wow, OK, this was a much more basic aspect of literacy – just being able to hear the sounds clearly.  So this is the case, apparently, for many bright and enthusiastic children, who experience difficulty in learning to read.  Without the basic perceptual tools to hear “ba” as different from “da” or “pa” or “ta” – the typical schoolday is for naught.

With this in mind, the recent article, “Genetic determinants of target and novelty-related event-related potentials in the auditory oddball response” [doi:10.1016/j.neuroimage.2009.02.045] caught my eye.  The research team of Jingyu Liu and colleagues asked healthy volunteers just to listen to a soundtrack of meaningless beeps, tones, whistles etc.  The participants typically would hear a long stretch of the same sound eg. “beep, beep, beep, beep” with a rare oddball “boop” interspersed at irregular intervals.  The subjects were instructed to simply press a button each time they heard an oddball stimulus.  Easy, right?  Click here to listen to an example of an “auditory oddball paradigm” (though not one from the Liu et al., paper).  Did you hear the oddball?  What was your brain doing? and what genes might contribute to the development of this perceptual ability?

The researchers sought to answer this question by screening 41 volunteers at 384 single nucleotide polymorphisms (SNPs) in 222 genes selected for their metabolic function in the brain.  The team used electroencephalogram recordings of brain activity to measure differences in activity for “boop” vs. “beep” type stimuli – specifically, at certain times before and after stimulus onset – described by the so-called N1, N2b, P3a, P3b component peaks in the event-related potentials waveforms.  800px-Erp1Genotype data (coded as 1,0,-1 for aa, aA, AA) and EEG data were plugged into the team’s home-grown parallel independent components analysis (ICA) pipeline (generously provided freely here) and several positives were then evaluated for their relationships in biochemical signal transduction pathways (using the Ingenuity Pathway Analysis toolkit.  A very novel and sophisticated analytical method for certain!

The results showed that certain waveforms, localized to certain areas of the scalp were significantly associated with the perception of various oddball “boop”-like stimuli.  For example, the early and late P3 ERP components, located over the frontal midline and parieto-occipital areas, respectively, were associated with the perception of oddball stimuli.  Genetic analysis showed that several catecholaminergic SNPs such as rs1800545 and rs521674 (ADRA2A), rs6578993 and rs3842726 (TH) were associated with both the early and late P3 ERP component as well as other aspects of oddball detection.

Both of these genes are important in the synaptic function of noradrenergic and dopaminergic synapses. Tyrosine hydroxylase, in particular, is a rate-limiting enzyme in catecholamine synthesis.  Thus, the team has identified some very specific molecular processes that contribute to individual differences in perceptual ability.  In addition to the several other genes they identified, the team has provided a fantastic new method to begin to crack open the synaptic complexities of attention and learning.  See, I told you learning to read was hard!

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