Representation of brief temporal patterns, Hebbian synapses, and the left-hemisphere dominance for phoneme recognition

Abstract

There is considerable evidence, including that from single-unit classical conditioning studies, that patterns that are briefly extended in time can be learned. Learning of simultaneous patterns is usually assumed to occur by strengthening of selected synaptic connections converging on single neurons. The present paper extends this principle to the learning of patterns that are slightly extended in time. Evidence is reviewed that cortico-cortical axonal connections impose a range of conduction delays sufficient to permit temporal convergence at the single-neuron level between signals originating up to 100-200 msec apart. By selection of appropriate connections, brief temporal patterns can be represented by converging connections with different conduction delays. The Hebbian postulate for synaptic modification is sufficiently precise in time to permit such selection. FinaIly, this hypothesis is applied to the learning of phoneme recognition in the human forebrain, and a suggestion is made concerning the biological basis of left-hemisphere dominance for phoneme recognition.

Reconstruction of ovine axonal cytoarchitecture enables more accurate models of brain biomechanics

“…2 a, b). Given the theory of cerebral laterality 44 , 101 , 102 , a conservative choice of sampling only from the left hemisphere has been taken to avoid any possible difference between left and right hemisphere. Additionally, to ensure a higher precision and a consistent repeatability in the sampling area, a custom-made brain slicer has been developed.…”