Neurophysiology of Learning

Abstract

The neurophysiology of learning can hardly be considered separately from the larger problems of neurophysiological mechanisms subs erving be havioral reactions in general. Learning is a concept which has meaning only in terms of performance of an organism, and performance is the integrated outcome of factors from all classes of psychological variables: receptor functions, motor functions, species-specific propensities and specific instinctive acts, and factors pertaining to motivational and emotional states of the organism. Experimental manipulation of the brain can affect all classes of variables related to behavioral performance, and neither our un derstanding of neurophysiology nor the specification of behaviorally defined functions is sufficiently precise to implicate uniquely a "learning process" as the critical event relating any brain-behavior relationship. This review assumes an expedient definition of its topic and emphazies primarily those studies in which acquisition or retention of learned responses is correlated with alterations in neuroanatomical or neurophysiological states. No sys tematic coverage has been made of the growing body of research data re lating learning and effects of neurotropic pharmacological agents. Herz (80) has recently reviewed work on drugs and the conditioned avoidance re sponse e CAR).Two books especially noteworthy for students of the neurophysiology of learning were published last year. As a tri b ute and memorial to K. S. Lash ley, four of his former students and colleagues have assembled and repub lished in book form a collection of 31 of his original papers [Beach et al. e 15) ]. Brief introductions by E. G. Boring and Stanley Cobb evaluate Lashley's contributions to psychology and neurology, respectively. This volume will perform a very useful function for the student and research worker in bringing together in an easily available form some of Lashley's Q 1 The survey of literature pertai ni ng to this review was concluded in April 1961.• Abbreviations used in this chapter include: ACh (acetylcholine); ChE (cholinesterase); CAR (conditioned avoidance response); CER (conditioned emo tional response) ; CR (conditioned response) ; CS (conditioned stimulus) ; RF re ticular formation ; SD (spreading depression); UR (unconditioned response); US (unconditioned stimulus) � EEG is used to refer to recordings of electrical activity of the brain from electrodes on the scalp or from implanted electrodes on the cortex or in subcortical structures.

Search for Correlations Between Genotypes and Electrophysiological Patterns in Migraine: The MTHFR C677T Polymorphism and Visual Evoked Potentials

“…In a recent cross-sectional study of individuals aged 50-70 years, the MTHFR TT variant was associated with better cognitive performance compared with CC or CT genotypes, an association which was not mediated by homocysteine concentrations or carotid intima-media thickness (42). Knowing the seminal role of habituation in learning processes (43), the question arises whether subjects with the TT genotype might perform better on certain cognitive tests because they habituate better during repeated sensory stimulation.…”

Cholinergic modulation of frequency receptive fields in auditory cortex: II. Frequency‐specific effects of anticholinesterases provide evidence for a modulatory action of endogenous Ach

“…Also, pairing one frequency with iontophoretic application of ACh produces receptive field modification that is specific to the paired frequency, and this effect is blocked by atropine (Metherate and Weinberger, 1989). Similarly, associative learning is accompanied by changed response in visual, somatosensory, and auditory cortex to stimuli which signal behavioral reinforcement (reviews: Kandel and Spencer, 1968;Thompson et al, 1972;Weinberger et al, 1984). Receptive fields have been studied in the auditory cortex during learning, and these modifications consist of maximal change at the frequency of the conditioned stimulus, often with simultaneous decreased response to adjacent frequencies (Bakin et al, 1988;Weinberger, 1986, 1989).…”

Garth J. Thomas, Physiological Psychologist: An Appraisal of His Contributions to Memory Research

“…By the time that Thomas wrote his review on the “Neurophysiology of Learning” [35], no systematic research had been carried out to elucidate the specific neural mechanisms of learning processes. The engram existed only as a speculation, as well as in anatomical theories, such as those of Hebb [36] and Konorski [37].…”

“…Thomas [35] also discussed other theories of learning, including the theory of protein molecules presented by Katz and Halstead [48], as well as the role of glia. Protein molecules were hypothesized to stimulate the engram, and information could be stored in neurons through excitation-induced specificity of ribonucleic acid molecules that would control the release of neurotransmitters to the postsynaptic membrane, whereas the glial theory suggested that astrocytes may play a substantial role in overall brain function, and, particularly, in long-term memory.…”

“…Three decades earlier, Thomas [35] had foreseen that learning could be understood only through the study of functions, such as instinctive and motor acts, or motivation and affective parameters. The research methods available at the time of Thomas' work were elaborate; he had expressed the hope that, in the future, with the evolution of technology, automatic devices would become available to make the appropriate measurements.…”