Amygdala modulation of visual cortex

Further evidence that the amygdala modulates visual cortex. Unfortunately, it is not unit recording, it is actually an optical imaging study. The study was performed in the cat under anesthesia, not ideal either.

Y. Chen, H. Li, Z. Jin, T. Shou, H. Yu (2013). Feedback of the amygdala globally modulates visual response of primary visual cortex in the cat. Neuroimage, in press.

Low road vs. multiple roads

The processing of affective information has many attributes that make it special, such as speed, and relative independence from attention and awareness. A key question, therefore, both from basic and applied perspectives is how this happens. An extraordinarily popular account is that a so-called low road from the retina via the superior colliculus and pulvinar conveys information to the amygdala. The general idea is that, because the pathway is entirely subcortical, processing would then be automatic.

This proposal has captured the attention of the research community and has fostered several lines of investigation — what is the role of attention, of awareness, how fast are certain effects, what type of visual information is conveyed (low vs. high spatial frequency), etc. Although these questions are interesting, the subcortical pathway idea is, in my view, largely based on an idea, rather than solidly grounded on empirical data.

So for a while now, Ralph Adolphs and I have been discussing what are serious problems with the notion of automatic subcortical processing of affective information. We have now written up some of these ideas in this Opinion piece in Nature Reviews Neuroscience. We also propose a new scheme, called the multiple-waves model that is intended to be an alternative to the “standard view”. It looks like part (B) of this figure, in contrast to the more traditional view shown in (A).

The proposal also incorporates the fact that the pulvinar is a highly integrative thalamic region, with extensive interconnectivity with much of cortex, as shown below.

The pulvinar works in a way that integrates cortical-subcortical processing.

Amygdala and attention

An extremely interesting aspect of amygdala function is that mild electrical stimulation of this structure produces an “orienting response”. As described originally by Kaada and colleagues, “the animal usually raises its head and looks in an inquisitive manner”. The original photos by Kaada are quite revealing, as shown here in this drawing.

Attention response

ATTENTION RESPONSE. Stimulation of the amygdala with mild electrical currents elicits an “attention response”. (A) Before stimulation. (B, C) During stimulation. Adapted from Ursin and Kaada (1960). Illustration by Gatis Cirulis.

I suggest that this behavior is a manifestation of affective attention processes carried out by the amygdala and related structures, including the basal forebrain and hypothalamus (paper). Whereas some of these mechanisms mobilize neural resources, others are suggested to engage bodily resources, too.

Affective attention.

AFFECTIVE ATTENTION depends on the amygdala (A; blue ellipse) and other structures. Diffuse projections from the basal forebrain are shown in yellow; efferent projections from amygdala nuclei are shown in green; the central nucleus of the amygdala also originates descending projections (black arrow) via the hypothalamus and other brainstem nuclei.

The amygdala: From “What is it?” to “What’s to be done” functions

In this Blog I will discuss ongoing issues related to cognitive-emotional interactions in terms of brain and behavior. Mostly, I’ll discuss some of my ongoing research and related ideas and, occasionally, I’ll write an entry related to other published papers of interest.

In this first post, I’ll comment on a recent review that I wrote trying to summarize some of the functions of the amygdala (here’s the link:  paper).

So, what is the function of the amygdala? Beyond the “fear theme” that has dominated research in the past several decades, two papers that were quite influential in proposing a broader role for the amygdala were the one by Paul Whalen in 1998 and the one by Sander and colleagues (2003). In my review, I suggest that it might be fruitful to go beyond what both of these papers suggested and to consider the roles of the amygdala more broadly in terms of attention, and the representation of value and decision making. Naturally, all of these ideas have been described in the past, but I give my angle on these and other issues in the review. I picked up on a them discussed by Pribram and McGuiness (1975) on conceptualizing functions in terms of “What is it?” and “What’s to be done?” roles that I believe are useful.

In the context of thinking of more general functions of the amygdala, a recent quote that I particularly like, which I recently came across, is one from Amaral and Price (1984), in which they suggest the following:

“As our knowledge of the connections of the amygdala has expanded, it has become apparent that the earlier view that it is primarily involved in the control of visceral and autonomic function is incomplete… These widespread interconnections with diverse parts of the brain simply do not fit with a narrow functional role for the amygdaloid complex. They support, rather, the behavioral and clinical observations which suggest that the amygdaloid complex should be included among the structures which are responsible for the elaboration of higher cognitive functions” (pp. 492-493).

Refs:

Amaral, D.G. & Price, J.L. Amygdalo-cortical projections in the monkey (Macaca fascicularis). The Journal of comparative neurology 230, 465-496 (1984).

Pribram KH, McGuinness D (1975) Arousal, activation, and effort in the control of attention. Psychol Rev 82:116-149.

Sander D, Grafman J, Zalla T (2003) The human amygdala: an evolved system for relevance detection. Rev Neurosci 14:303-316.

Whalen PJ (1998) Fear, vigilance, and ambiguity: Initial neuroimaging studies of the human amygdala. Current Directions in Psychological Science 7:177-188.