Brain Mechanisms of Learning and Cognition: An Overview

Across this chapter you read about brain mechanisms for selected learning and cognitive phenomena as studied mainly in mammals. In each case, only some of the components of the circuitry underlying a particular phenomenon were introduced. You may have noticed that there is overlap in the brain regions that participate in these phenomena (Figure 6.21). In terms of learning and cognition, a major difference between simple systems (see Chapter 4) and the more complex brains of vertebrates (see Chapter 5) is the degree to which the neural circuitry is distributed. This chapter makes it clear that understanding behavioral plasticity in vertebrates requires a consideration of circuitry, that is, how a collection of brain areas interact to generate an output. In some isolated cases (notably in fear conditioning), advances in research make it possible to understand some of the processing that takes place within a single area (e.g., the amygdala). The mapping of behavioral concepts into brain circuitry is therefore more complicated than it appears at first sight because the function is distributed over several brain regions.

Moreover, specific regions are engaged by different phenomena. The amygdala, for example, which seems critical for fear and avoidance conditioning, also participates in schedule-induced polydipsia, a seemingly disparate function. The cerebellum, here noticed in connection to interval timing, is also involved in motor learning (see Figure 5.9). Moreover,

Figure 6.21 A summary of brain areas cited in relation to specific learning phenomena in this chapter.

neurons within a single area can be important for different functions. For example, within the basolateral amygdala (BLA), neurons responding to signals for sucrose (appetitive) project to the nucleus accumbens (NAc), whereas those responding to quinine (aversive) project to the central amygdala (CeA) (Beyeler et al., 2016). Thus, the BLA-^NAc pathway encodes information with positive valence, whereas the BLA-^CeA pathway is concerned with signals of negative valence. The fact that these neurons coexist in the same location makes it simplistic to assign a single function to a given brain area.