The Operation of Memory Systems in the Brain - Computational Neuroscience: A Comprehensive Approach - page 518

VISION

Inferior temporal
visu al cortex V1 V2 V4

Amygdala Striatum

TASTE

Taste
receptors

Nucleus of the
solitary tract

Thalamus
VPMpc nucleus

Lateral
hypothalamus

Gate
function

Frontal operculum/insula
(primary taste cortex)

Gate
Orbitofrontal
Cortex

Hunger neuron
controlled by, e.g.,
glucose utilization,
stomach distension,
or body weight

OLFACTION

Olfactory
bulb

Olfactory (pyriform)
cortex

Insula

TOUCH

Thalamus VPL Primary somatosensory cortex (1.2.3)

Figure 16.14
Diagrammatic representation of some of the connections described in this chapter.
V1, striate visual cortex. V2 and V4, cortical visual areas. In primates, sensory
analysis proceeds in the visual system as far as the inferior temporal cortex and the
primary gustatory cortex; beyond these areas, in for example the amygdala and or-
bitofrontal cortex, the hedonic value of the stimuli, and whether they are reinforcing
or are associated with reinforcement, is represented (see text).

include the ability of a perceptual input to trigger a mood state in the 'amygdala'
module if there is not an existing mood, but greater difficulty to induce a new mood
if there is already a strong mood attractor present; and the ability of the mood to
affect via the backprojections which memories are triggered.
An interesting property which was revealed by the model is that because of the
many-to-few mapping of perceptual to mood states, an effect of a mood was that
it tended to make all the perceptual or memory states associated with a particular
mood more similar then they would otherwise have been. The implication is that
the coupling parameter g for the backprojections must be quite weak, as otherwise
interference increases in the perceptual / memory module (IT in Figure 16.15).
Acknowledgments : This research was supported by Medical Research Council Pro-
gramme Grant PG9826105, by the MRC Interdisciplinary Research Centre for Cog-
nitive Neuroscience, and by the Human Frontier Science Program.