Happy same-race face familiarity and the right ventral stream

I have often extolled the ideas of polymodality or association, that the brain does not maintain a one-to-one structure-function correlation, and in visual processing this is also the case (see also Zillmer, Spiers, & Culbertson, 2008). While there is not a common visual processor, despite the name “occipital lobe,” there does exist a “seemingly instantaneous… culmination of separate but locally connected visual-perceptual processes” (p. 200). Not only are these seemingly instantaneous processes happening linearly, they also happen in parallel, giving us what is called bottom up percept formation and top-down building, though the latter is a matter of debate (p. 200).

I might like to include a word or two from a previous post in response to another learner about polymodal circuits in the brain.

The “what” pathway is occipital input along the occipital-temporal (associational) pathway to the inferior temporal region, helps us to recognize objects and perceive things (Zillmer, et al., 2008, p. 160; and for a great discussion on autism spectrum disorders and the Fusiform Face Area or FFA which is part of the social-emotional brain/circuit, which includes, amongst other regions, temporal, frontal, and limbic/other subcortical nuclei, see pp. 316-18). The “where” pathway, which, as you might guess, is similar occipital input orients more to the occipital-parietal pathway and to the posterior parietal lobe, processes this way to give us “where,” or spatial recognition. (Brown, post to a colleague on Capella course page, 2009).

In this post, I will cover one article on the neural correlates of same-race face recognition using positive/happy stimuli. The study in question demonstrated that same-race faces showing positive stimuli (in this case, three races where used, Japanese – the participants were all Japanese – other Asian, and Caucasian) positively correlate to greater amygdalic, posterior cingulate cortex (PCC), and superior temporal gyrus (STG) (the STG because these same-race faces where subjectively more familiar than the others) (Iidaka, Nogawa, Kansaku, & Sadato, 2008, p. 91). These results were also corroborated in many other studies that the authors thoughtfully cited and from which they drew a very clear, logical pattern and generated hypotheses.

Additional findings included that “the PCC is the neural correlate that is specifically involved when the Japanese subjects judge the happy expression on a same-race face;” that the amygdala responded to the presentation of both positive and negative emotional content; that the superior temporal sulcus (STS) is more active when greater personal familiarity is present in the stimulus; that “regions adjacent to the posterior STS may play a similar role as the PCC with regard to the same-race face processing;” and lastly, that because the PCC is implicated in memory retrieval, this region is thought to correlate to a sense of familiarity when the subjects viewed a happy face from their own race (pp. 97-8).

So, what goes wrong when lesions to these areas of the brain occur? Typically, these disorders are referred to as apperceptive and associative visual agnosias, such as prosopagnosia or the inability to recognize people by their faces (Zillmer, et al., 2008, p. 207). While prosopagnosia is thought to be a disorder of higher order processing relayed through the thalamus (p. 204), it is clear that the “what”/ventral stream, a stream that helps to connect visual perception with meaning (p. 206), receives impulses from the subregions of the visual association cortex, the V2 area, and the striate cortex (Carlson, 2010, p. 196). The left hemispheric ventral stream is associated with letters and numbers (symbols) whereas the right is more specific to recognition of faces and other objects (Zillmer, et al., 2008, p. 207). Damage to the right side can result in visual agnosia, such as prosopagnosia; whereas left sided damage results in neglect and problems distinguishing between left and right (p. 207). Cognitive neuropsychologists generally classify these agnosias into two groups: apperceptive visual agnosias (problems with object perception – like seeing in bits and pieces) and associative visual agnosias (problems assigning meaning to objects) (p. 207). If both hemispheres are involved, Balint’s syndrome may be involved, which includes visual agnosia with visuospatial difficulties such as mis-reaching and neglect (p. 207).

These ideas are fascinating in their polymodality and association in tandem, often overlapping, parallel streams. I might pose the following questions for thought: how can researchers acknowledge polymodality, while noting the relative unitariness of various constructs such as “problems differentiating left from right” or degree of happy, same-race face familiarity? Does this have some implication for the physico-behavioral mapping of continuous neurophysiology? What are the implications of extra-regional lesion – that is, when the boundaries of a lesion exceed the region’s known, discrete function?
These and other questions will perhaps keep you up tonight. Rest assured, however, there will be another day to explore this wild west of science.


References

Carlson, N. (2010). Physiology of behavior, (10th ed.). Boston: Allyn & Bacon.

Iidaka, T., Nogawa, J., Kansaku, K., & Sadato, N. (2008). Neural correlates involved in processing happy affect on same race faces. Journal of Psychophysiology, 22(2), 91-99. doi:10.1027/0269-8803.22.2.91

Zillmer, E., Spiers, M., & Culbertson, W. (2008). Principles of neuropsychology, (2nd ed.). Belmont, CA: Thomson Wadsworth.