Three-dimensional estimation of the distribution and size of putative functional units in rat gustatory cortex as assessed from the inter-neuronal distance between two neurons with correlative activity.
Two neurons recorded simultaneously in rat gustatory cortex often show, when the oral mucosa is stimulated with effective taste solutions, correlative activities (CAs), which can be quantified with a cross-correlation technique. It has been suggested that the CAs are involved in taste quality discrimination and the neuron pairs with CA (CA pairs) may function as a unit (putative functional unit). The present experiment was undertaken (1) to determine the three-dimensional size of putative functional units in rat gustatory cortex on the basis of the interneuronal distance (IND) in individual CA pairs, and (2) to examine to what extent the CA is related to the intrapair similarity in taste responses. The findings were as follows: (1) The CAs occurred in 30 out of 55 pairs with INDs < or =270 microm and often at INDs <100 microm. (2) The numbers of putative functional units were calculated tentatively by using the longest or the mean INDs; at least 200 or over 4,000 units, respectively. (3) In the CA pairs, the "best taste" was identical (homo-type) in many pairs, the "taste profiles" were often similar, and the temporal courses of taste responses resembled each other in more than one half of the pairs. A possible role of hetero-type pairs was discussed. (4) In a small number of cases, troughs were observed in the CCs, suggesting the involvement of local inhibitory neurons. In conclusion we point out that nearby neurons are prone to CA, if (1) their best tastes are identical, (2) their taste profiles are similar, and (3) the temporal patterns of taste response resemble each other.
Yokota
T
T
Department of Physiology, School of Dental Medicine, Aichi-Gakuin University, Nagoya, Japan. tyokota@dpc.aichi-gakuin.ac.jp
Satoh
T
T
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D013268:Stimulation, Chemical; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D013649:Taste / Q000187:drug effects / Q000502:physiology*; D013650:Taste Buds / Q000187:drug effects / Q000502:physiology