Effect of Local Synaptic Strengthening on Global Activity-Wave Growth in the Hippocampus

• Published in: International journal of neuroscience Vol. 108; no. 1-2; pp. 127 - 146
• Main Authors: Koch, Paul, Leisman, Gerald
• Format: Journal Article
• Language: English
• Published: London Informa UK Ltd 01.01.2001; Taylor & Francis
• Subjects: Animals; Biological and medical sciences; Cell assemblies; Cell physiology; Continuum theory; Fourier Analysis; Fundamental and applied biological sciences. Psychology; Hippocampus; Hippocampus - cytology; Hippocampus - physiology; Humans; Mathematics; Memory; Memory - physiology; Miscellaneous; Models, Neurological; Molecular and cellular biology; Neural networks; Neurons - physiology; Synapses - physiology; Alpha rhythm; Acquisition process; Memory; Central nervous system; Synaptic inhibition; Mathematical model; Long term; Summation; Hippocampus; Brain (vertebrata)
• ISSN: 0020-7454; 1563-5279; 1543-5245
• DOI: 10.3109/00207450108986510

Analysis of a continuum model of the hippocampus shows that strengthening of the synaptic connections within localized regions can convert the global activity-wave properties from decay to growth. These growing waves can play a part in the implantation of long-term memory in the higher brain regions. The wavelength of the fastest-growing mode decreases with increasing local synaptic strength and can be modified by the chemical state as reflected by synaptic sensitivity to stimuli. The temporal period of the response is a constant, equal to twice the delay time exhibited by some of the hippocampal inhibitory neurons ("d-cells"). The value for the period obtained from this relationship and measurement of the delay time agrees with the hippocampal gamma rhythm. For normal hippocampal function the proportion of d-cells is limited to one-third the total number of inhibitory neurons.