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Karl Spencer Lashley (1890–1958)
Published in Andrew P. Wickens, Key Thinkers in Neuroscience, 2018
On the basis of these findings, Lashley derived two general laws about the cortical basis of learning and memory: (1) learning is mediated by the whole cerebral cortex and stored in neural circuits that are widely and diffusely distributed – a principle he called mass action and (2) all parts of the cerebral cortex play an equal role in the storage of memory (which in effect means all of its regions are equally able to perform a task) – a principle he called equipotentiality. These two laws implied that the neural correlates of learning were stored everywhere or no place in particular. Moreover, they not only refuted Pavlov’s stimulus-response theory of cortical function but also dealt a serious blow to the assumptions of behaviourism with its simple emphasis on explaining behaviour in terms of conditioned reflexes.
Disorders of Sensation, Motion, and Body Schema
Published in Rolland S. Parker, Concussive Brain Trauma, 2016
Cortical reorganization (plasticity) affects multiple levels of the somatosensory pathway. The loss of one link disturbs the functional system as a whole. Patterns of recovery have been described: compensation and substitution of function (new responses to solve tasks); equipotentiality and vicariation (if specific lesions do not cause a specific deficit, other areas are said to “take over” the function); diaschisis (Bach-Y-Rita, 2002) (at sites distant to the injury there is depressed metabolic activity or reduced neuronal activity). Examples include crossed-cerebellar inhibition, and interaction between the locus ceruleus and the ipsilateral sensorimotor cortex. During attempted repair, the undamaged terminals elsewhere may not function normally; reorganization or unmasking of “latent synapses (expansion of cortical receptive fields; synesthesias, phantom limb reactions, and visual stimulation activating the auditory cortex, and vice versa).
The Return Of The Reflex
Published in Andrew P. Wickens, A History of the Brain, 2014
On the basis of these experimental findings, Lashley devised two general laws about the localisation of the engram which he outlined in his book Brain Mechanisms and Intelligence: (1) memory is stored throughout the cerebral cortex – a principle he called ‘mass action’; (2) all parts of the cortex play an equal role in the storage or memory – which he called ‘equipotentiality’. It was as if the neural correlates of maze learning were stored everywhere or no place in particular – a finding not explainable in terms of Pavlov’s theory. It also led Lashley to reject the assumptions of behaviourism with its simple emphasis on explaining all behaviour in terms of conditioned reflexes. Another problem with the conditioned reflex concept was that many types of skilled behaviour such as playing a musical instrument were simply too fast for them to be directed by a chain of stimulus–response actions (a golf swing, or a tennis player attempting to return a high velocity serve are two other examples). Consequently, Lashley reasoned they had to be ‘centrally supervised’ in some other way. Thus, there must be a more complex representation in the brain, or ‘schemata of action’ which was able to generate behavioural responses independently of any stimulus. However, he was never able to provide a convincing explanation for the phenomena. After some 30 years of research, Lashley was to conclude in, in a paper entitled In Search of the Engram, that despite all his attempts to localise the memory trace, he had not been able to do it.
Nineteenth- and twentieth-century brain maps relating to locations and constructions of brain functions
Published in Journal of the History of the Neurosciences, 2022
During the intervening years, new approaches required new brain maps to illustrate them. Initially, the equipotentiality approach associated with French physiologist Marie Jean Pierre Flourens (1794–1867) effectively countered a localization approach until the electrical stimulation results of Gustav Fritsch (1838–1927) and Eduard Hitzig (1838–1907) and those of David Ferrier (1843–1928) (Flourens 1824, 1842; Young 1970). As will be illustrated in this article, their probes gave rise to new brain maps and gave a new reason to study and delimit cerebral convolutions. In the mid-twentieth century, the studies of Wilder Penfield (1891–1976) enhanced interest in this localization approach and required yet another type of brain map—one to capture its complexity and organization. A separate strand of the essay tied to the first, because of the growing realization that mental processes could be natural processes, discusses the clinical approaches of Carl Wernicke (1848–1905) and Ludwig Lichtheim (1845–1928), which eventually lead to further advances by Geschwind and his associates in the twentieth century. Their brain maps attempted to show that mental processes originated in interacting subprocesses. The article ends with an acknowledgment that fMRIs and PET scans add a new dimension to brain maps and to mental processes.
The Non/Inhuman Within: Beyond the Biopolitical Intrauterine Imaginary
Published in Studies in Gender and Sexuality, 2021
An important thinker to pay attention to the early embryo process was Raymond Ruyer in The Genesis of Living Forms (originally published in French in 1958; see Ruyer, 2019). In his work on the philosophy of biology, Ruyer explores embryogenesis as a formative process that is inherently one of connectedness (to the female body) and autopoiesis. He refers to the process as equipotentiality, and one that is affective, referring to it as a melody that controls development and as such is key to understanding life, such that it unfolds over time with its ability to make itself from the placenta material.3This legacy of this can be seen in Luce Irigaray’s work on the placenta in Je, Tu, Nous: Towards a Culture of Difference (Oele, 2007), as well as the writing of other thinkers who work with the placenta and its materialization with the embryo and its function within embryogenesis, through to the development of the fetus; for example, see, Laura Bollinger, Placental Economy: Octavia Butler, Luce Irigaray, and Speculative Subjectivity (2007), Laura Green, “Myths, Matricide and Maternal Subjectivity in Irigaray” (2012), and Marjolein Oele, “Openness and Protection: A Philosophical Analysis of the Placenta’s Mediatory Role in Coconstituting Emergent, Intertwined Identities” (2017). From Ruyer’s embryogenesis, all life is at once the same and constantly changing.