Donald Olding Hebb, referred to by American Psychologist as one of "the 20th century's most eminent and influential theorists in the realm of brain function and behavior," contributes greatly to the understanding of mind and thought in Essays on Mind. His objective was to learn about thought which he considered "the central problem of psychology -- but also, not less important, to learn how to think clearly about thought, which is philosophy." The volume is written for advanced undergraduates, (...) graduates, professionals, and lay people interested in or studying the mind. Hebb offers an increased understanding of the mind from a biological perspective that affects long-standing philosophical and psychological problems. "Psychology and Philosophy were divorced some time ago but, like other divorced couples, they still have problems in common," writes Hebb. The first three chapters establish the methodological and philosophical basis for his biologically centered theory of behavior, including the evolution of the mind, nature versus nurture, the origination and status of cell-assembly theory, and infant thought and language development. He concludes with a discussion of the workings of scientific thought from a practical rather than theoretical perspective. (shrink)
Brain rhythms are more than just passive phenomena in visual cortex. For the first time, we show that the physiology underlying brain rhythms actively suppresses and releases cortical areas on a second-to-second basis during visual processing. Furthermore, their influence is specific at the scale of individual gyri. We quantified the interaction between broadband spectral change and brain rhythms on a second-to-second basis in electrocorticographic (ECoG) measurement of brain surface potentials in five human subjects during a visual search task. Comparison of (...) visual search epochs with a blank screen baseline revealed changes in the raw potential, the amplitude of rhythmic activity, and in the decoupled broadband spectral amplitude. We present new methods to characterize the intensity and preferred phase of coupling between broadband power and band-limited rhythms, and to estimate the magnitude of rhythm-to-broadband modulation on a trial-by-trial basis. These tools revealed numerous coupling motifs between the phase of low frequency (δ, θ, α, β, and γ band) rhythms and the amplitude of broadband spectral change. In the θ and β ranges, the coupling of phase to broadband change is dynamic during visual processing, decreasing in some occipital areas and increasing in others, in a gyrally specific pattern. Finally, we demonstrate that the rhythms interact with one another across frequency ranges, and across cortical sites. (shrink)
Introduction to sensory psychology, by C. Mueller.--Some reflections on brain and mind, by R. Brain.--In search of the engram, by K. Lashly.--Cerebral organization and behavior, by R. W. Sperry.--Relations between the central nervous system and the peripheral organs, by E. von Holst.--Effects of the Gestalt revolution, by J. E. Hochberg.--Seeing in depth, by R. L. Gregory.--The stimulus variables for visual depth perception, by J. J. Gibson.--The elaboration of the universe, by J. Piaget.--Visual perception approached by the method of stabilized images, (...) by R. M. Pritchard, W. Heron, and D. O. Hebb.--Philosophy as rigorous science, by E. Husserl.--The "sensation" as a unit of experience, by M. Merleau-Ponty.--The phenomenology of perception: perceptual implications, by A. Gurwitsch.--The expression of thinking, by E. W. Straus.--The concept of group and the theory of perception, by E. Cassirer.--Norm and pathology of I-world relations, by E. W. Straus.--The metaphysical in man, by M. Merleau-Ponty.--Cultural differences in the perception of geometric illusions, by M. H. Segall, D. T. Campbell, and M. J. Herskovits.--The interpretive cortex, by W. Penfield.--Recovery from early blindness: a case study, by R. L. Gregory and J. G. Wallace.--Visual disturbances after perceptual isolation, by W. Heron, B. K. Doane, and T. H. Scott. (shrink)
The self, Joseph LeDoux tells us, is “the totality of the living organism”. Most disciplines in the natural sciences focus on only one or two levels of organization. Indeed, Dmitri Mendeleev figured out the periodic table of the elements without knowing any of the underlying quantum mechanics or stereochemistry. There are, however, at least a dozen levels of organization within the neurosciences — and, if we use a metaphor, we temporarily create yet another. This leads to considerable confusion and arguments (...) at cross purposes over whether learning is an alteration at the level of gene expression, ion channels, synapses, neurons or circuits. Each neuron has thousands of synapses, which produce currents that summate to form an impulse train. But only rarely is the activity of a single neuron sufficient to cause a perception or trigger an action. Neurons usually act as members of ‘committees’ — what DonaldHebb in 1949 called cellassemblies. Just as in academia, one individual may function in different committees on different occasions. A concept, including any explicit memory that we can talk about, is probably formed by such a committee. Implicit memories (the ones you can’t talk about) are less differentiated — they are part of the ‘feltwork’, together with motivations and emotions, that biases the choice of one’s next act. In this well-written 400-page appreciation of behavioural neuroscience, LeDoux argues that synapses are the seat of self. He says, in effect, that you are your memories; that it is the uniqueness of an array of synaptic strengths that distinguishes one twin from another. Fair enough, but why not instead focus on one’s unique array of ion channels? Or neurons, because a neuron is the closest thing we have to a computational unit (synapses have to reach a threshold before they have any influence at all)? Or one’s unique arrangement of those overlapping, redundant hebbian committees? None of these make for a catchy book title, but relating other things to the synapses proves to be a good way of covering a lot of fascinating material at the overlying levels, including a few updates to LeDoux’s earlier book The Emotional Brain (Simon & Schuster, 1996).. (shrink)
We briefly review the long-standing ideas about the use of synchronicity in the brain, which rely on DonaldHebb's views on cell assemblies and synaptic plasticity. More recently the distinction among several timescales in the description of neural activity has become a focus of theoretical discussion. Phillips & Singer's target article is criticized mainly because it does not distinguish these timescales properly and hence does not really address the questions so intensely debated today.
The HIT model comes close to a view suggested by DonaldHebb, that cognitive representations are organized as distributed neuron webs, cell assemblies, whose components are mutually connected and whose internal connections provide continuous information exchange among sub-components of the representation. Two questions are asked related to (1) the organization of internal connections of a concept representation and (2) the conditions under which information exchange between components are assumed in the HIT model.