After Phrenology: Neural Reuse and the Interactive Brain by Michael L. Anderson (review)

After Phrenology by Michael L. Anderson is a unique and thoughtprovoking contribution to the current debate on how cognition interfaces with the environment and how we can move scientific studies of the brain forward. His theory of “neural reuse” is a proposal for how we may reframe the debate and fills in some of the gaps that exist now when we communicate about the mind, the brain and the environment. The basic idea is that, rather than seeing localized areas of brain activity as the way to define brain functionality, we should investigate the neural circuitry combinations that are employed to perform complex functions. Included in this notion is recognizing that our ways of doing things are both active and environmentally connected. For Anderson, “the Modern, Modular, cognitivist assumptions that have guided research during most of the last 50 years of cognitive neuroscience have not been borne out by the data this research produced” (pp. 301–302), and thus this book is a call for a new kind of approach—neural reuse. He additionally offers a theoretical framework that claims to show how this design offers an evolutionarily informed framework, one that has the capacity to both explain brain functions and recognize our embeddedness in our environments.

Anderson’s theoretical effort centers around the following concepts: (1) individual regions of the brain are functionally diverse and differentiated; (2) there is frequent functional overlap between different brain networks; (3) the brain is fundamentally action oriented and specializes in managing the organism’s interactions with the world; and (4) the brain achieves its functions by assembling the right functional coalitions between both neural and extraneural partners, supporting interaction with external artifacts—including symbolic ones—for cognitive ends. In making his points, Anderson asserts that contemporary cognitive neuroscience’s core view is that the brain is an informational processing device and studies too often rely on the notion of localization.

I suppose time will tell if “neural reuse” can aid in focusing discussions more on the use of local regions of the brain for multiple tasks across domains. Evidence Anderson points to includes examples like Broca’s area, which is fairly well established as a language region despite the frequency with which it is activated in nonlanguage tasks. Since seeing neural reuse as a fundamental feature of the functional architecture of the brain would allow us to rethink how we speak of the architecture, the categories used and even the principles of brain evolution and development, this kind of framework would, according to Anderson, better convey that Broca’s area is not only a language region. Admittedly, at the end, I was never really clear as to why he calls his viewpoint “neural reuse,” although it seems the concept is intended to convey functional overlap.

The best sections of the book are at the beginning, where Anderson lays out the evidence showing that individual regions of the brain are functionally diverse and are used and reused in many different tasks across cognitive domains. His first major point is that achieving functional specificity is a matter of assembling the right coalition of neural partners to accomplish the task in question. With this underpinning, he argues that this kind of functional structure makes evolutionary sense in terms of the efficient use of metabolically expensive and relatively scarce neural resources. Following this overview, Anderson turns to the functional development of the brain. Rather than positioning himself in terms of a more traditional functional specialization approach, he develops an argument for interactive differentiation as the relevant operational concept controlling development.

Overall the book argues that the brain is best understood as an action controller, responsible for managing the values of salient organismenvironment relationships (p. xxii). Thus, the multidimensional neural dispositions should be understood as the brain’s differential propensities to influence the organism’s response to the various features or affordances in its environment. In other words, each brain region is...