'The Entangled Brain' by Luiz Pessoa, a book review by Brenda Walker

20th Nov 2023

BNA associate member, Brenda Walker, shares her review of the book The Entangled Brain, How Perception, Cognition, and Emotion are woven together, by Luiz Pessoa.

Professor Pessoa is the plenary speaker at the BNA 2023 Festive Symposium 'Unwrapping the Neuroscience of Emotions' taking place on 11th December in London. 

An expensive book for a paperback but a cheaper, kindle version is also available; either well worth the money.

At the end of my last review for the associate membership of the British Neuroscience Association, I quoted Mike Tranter’s comment, ‘Science never sleeps’. That is certainly well illustrated in Luiz Pessoa’s ‘The Entangled Brain’ published by MIT Press in November 2022. The book’s sub-title is ‘How Perception, Cognition, and Emotion are woven together’, and the ‘How’ is expressed in a compelling, easy to read style that is never boring.  Neuroscience is stated to be going through a methodological renaissance and we are invited to ‘think outside the box’.

Pessoa’s enthusiasm for his ‘favourite topic’ permeates the text and makes reading a pleasure. He admits the study of the brain is complicated, but for those readers who are used to publications or media articles conveying ‘grey matter’ neurons as individual functioning units, this 267 page volume with 12 chapters, discards that traditional viewpoint and explains brain structure not as regions, but as an interaction of multiple parts: a network of layers of neurons, many exhibiting two-way conversations, creating a ‘close relationship’ linking perception, action, cognition and emotion; the network being the unit.

Explanations abound even in his personal and interesting preface, and throughout the volume his student-oriented teaching techniques shine; such as when he uses either unusual vocabulary (epistemically); unfamiliar terminology (Network Science); or anatomical terms (white matter tracts). At the end of the first chapter he describes the road ahead, describing how he intends to guide our thoughts towards considering the brain as a dynamic, complex, entangled system, but for those readers without a scientific background he begins with the naming of parts and the defining of terms, deeming them necessary starting points on the journey to building an appropriate vocabulary.  

The second chapter introduces general principles and enough anatomy to be able to follow the routes and points of interest. Pessoa stresses his central thesis that behaviours do not reside in one place and that having located an area of interest, it is necessary to explore ‘a gradually expanding circle of areas to which it is connected’.  He also helps the reader by providing a brief colloquial introduction to each chapter as well as an excellent final summary often ending with a motivational springboard phrase: ‘This is not just the case for the human brain but across all vertebrates – even “simple” ones.’ For example, the next chapter is entitled ‘The Minimal Brain: Building Simple Defences and Seeking Rewards’. ‘The Entangled Brain’ is clearly illustrated, has a glossary, pages of footnotes and a  text densely packed with information revealing a time line detailing earlier research with relevant key names and anecdotes. The importance of magnetic resonance imaging (MRI) is explained as well as the role of mathematical and computational tools now available to the researcher as Pessoa takes us into the wider biological world, referencing ecology, evolution and homology.  In explaining what brain areas actually do, he first discusses the older traditional assumption that they are modular in essence; “one area, one function”. Then, as often happens throughout the book while pointing out perceived flaws in earlier theories, he throws the reader a question. Although well set out, the text is occasionally dense with facts and the uninitiated will sometimes need to pay careful attention to paragraphs where ‘old’ thinking is discussed in close proximity to the new.

Following ‘What do brains do?’ chapter headings give a clear indication of Pessoa’s route map:

• Emotion and Motivation: The Subcortical Players
• Emotion and Motivation: The Cortex Comes to the Party
• Cognition and the Prefrontal Cortex
• Complex Systems: The Science of Interacting Parts                               
• 500 Million Years of Evolution                                        
• The Big Network: Putting Things Together
• Unlearning Fear
• It’s All about Complex, Entangled Networks

Many of the terms found in the above are more likely to be familiar from general usage: hubs, signals, communities, associations, attributes, clusters, trajectories, communications, systems, subsystems, networks, mechanisms, areas, regions, circuits, loops, units, computational properties etc., but Pessoa looks for answers not only in biology and ecology, but also in genetics, physics, mathematics, artificial intelligence, cybernetics and philosophy. Such vocabulary enables the reader to participate in the author’s theoretical understanding, for it is Pessoa’s firm belief that the only way to fully explain the cognitive-emotional brain is to ‘dissolve its boundaries’ and bring down the walls between subject areas. He calls for future research to develop a science of the ‘mind-brain’ using computational and mathematical tools now at their disposal, which if used integrally with conceptual and theoretical clarity, could move neuroscience research forward.

Throughout this iconoclastic volume, the concept of the brain as a sophisticated complex system is illuminated by real life examples which can tempt readers to reflect on aspects of their own life experiences regarding working memory, attention, motivation, action or fear. For instance, unlearning fear is described as an example of ‘extinction learning’, and said to occur when cognition inhibits emotion. In a summary, Pessoa writes:

‘Extinction’ is more than a simple form of inhibition. It is a sophisticated form of learning, and as such the formation of an “extinction memory” involves processes akin to those observed in learning in general: acquisition, consolidation, and retrieval. What is being learned is safety.

I quote in full because it exemplifies the brain supporting our perceptions, actions, thoughts and feelings; in other words - the mind.  Also, the detailed explanations in the book following this quotation are extremely relevant to what is happening in today’s world.

New data is continuing to be written about research involving mice or rats and although certain ethics are acknowledged, it is a little disconcerting to realise that within the last ten decades neuroanatomists have discovered the general plan of the brain in all vertebrates to be ‘strikingly similar’ to that of humans. Having read this, and in the light of your understanding of the central nervous system (CNS), your curiosity  may lead you to closer observation of the goldfish or birds you feed!

Luiz Pessoa states that he wrote this book so as to ‘build up the need to consider the brain as a complex entangled system’. He has certainly achieved his aim and now it is up to others, from all related subject areas, to use this foundation when considering further research.  In his own words:

 ‘Exciting days lie ahead of us’.      

Brenda Walker          November 2023