The responses of 111 cortical neurons to the four classical taste stimuli (sucrose, NaCl, HCl, and quinine HCl) applied to the anterior part of the tongue were recorded extracellularly in lightly anesthetized rats. Basic response properties of these cortical taste neurons were analyzed. The location of 88 of 111 neurons were histologically identified. They were distributed from anterodorsal to posteroventral direction in the insular cortex just dorsal to the rhinal sulcus and ventral to the somatic sensory area I. The receptive fields of 17 cortical neurons were examined. Most (94%) of the neurons had a narrow focus on the ipsilateral, contralateral, or bilateral sides of the tongue surface. Half of the foci were surrounded by a less-sensitive receptive field of relatively wide size. No apparent relationship was detected between the location of the cortical neurons and the site or extent of the receptive fields of those neurons, indicating a lack of topographical organization in the cortical gustatory area. The mean rate of the spontaneous discharges was 7.1 impulses/3 s, which is about 3 times larger than that in a first-order taste nerve (chorda tympani). The statistically significant difference of spontaneous discharges among response types of cortical neurons was observed only between the neurons responding in an excitatory manner to only one or two kinds of basic stimuli (6.2 impulses/3 s) and the neurons responding in an inhibitory manner to more than three kinds of taste stimuli (14.2 impulses/3 s). When the net responses (spontaneous rate subtracted) to each of the four tastes were compared with the spontaneous discharges in each neuron, the magnitude of spontaneous discharges was significantly negatively correlated with the net response to sucrose. This fact indicates that a neuron with a larger spontaneous discharge rate has a tendency to respond less to sucrose. Response characteristics of cortical taste neurons were quite distinct from those of the first-order taste neurons in the following respects: 1) a decrease in the average evoked discharge rate, which resulted in a small signal-to-noise ratio; 2) a tendency toward equalization of effectiveness of the four basic taste stimuli; 3) about 27% of the neurons decreased their firing rate during the first 3 s after the onset of taste stimulation; and 4) no clear initial phasic response, with a fluctuation in impulse discharges in some neurons.(ABSTRACT TRUNCATED AT 400 WORDS)
The responses of 39 cortical neurons to 13 kinds of taste stimuli including the four putative basic taste solutions (sucrose, NaCl, HCl, and quinine HCl) applied to the anterior portion of the tongue were recorded extracellularly in lightly anesthetized rats. The neural responses were analyzed in terms of the four hypotheses of quality coding: across-neuron response pattern, labeled-line, matrix pattern, and across-region response pattern notions. Animals were given a conditioned taste aversion to one of the 11 stimuli by pairing it with a gastrointestinal illness caused by intraperitoneal injection of 0.15 M LiCl. Behavioral taste profiles were constructed for each stimulus from the suppression of rate of drinking, which indicates the extent of generalization of aversion to each of the four basic taste stimuli. Neural taste profiles of each taste stimulus, which indicate the relation of the taste of a stimulus to each taste of the four basic stimuli, differed more or less depending on the kind of quality-coding notions employed. Among the four analyses, across-region correlation coefficients that were derived from an across-region response-pattern theory showed the highest correlation with the behavioral suppression rates. Therefore we conclude that processing of taste information in the cortex involves differences in both response magnitude across neurons and the spatial localization of those neurons. Fluid intake per day of each of the 12 taste solutions was measured by the single-bottle preference method. When the amount of intake was described in terms of an hedonic index (HI), which indicates the hedonic aspect of the taste of each solution, HI's for sucrose, NaCl, HCl, and quinine were 1.17, 0.43, -0.49, and -0.89, respectively. These values represent the degree of deviation of solution intake above (i.e., preferable) or below (aversive) the standard water intake. Then, HI's were calculated for each of the 12 taste stimuli based on the neural taste profiles and actual HI's for each of the four basic taste stimuli. The correlations between the calculated and the actual (or behaviorally obtained) HI's were very high (ranging from 0.832 to 0.941). This result suggests that the hedonic dimension of taste can be matched well by any one of the four proposed hypotheses.
We counted the number of toluidine blue positive mast cells within and around the tumor in 44 patients with soft tissue sarcomas (STS). Irrespective of their histologic types, these cases were broadly divided into the following two groups: (1) low count (less than 20 mast cells/10 high-power fields [HPF]) and (2) high count (greater than or equal to 20 mast cells/10 HPF). The patients with a high mast cell count showed a significantly better 5-year survival rate than those with a low count (85.9% versus 30.5%; P less than 0.01). Five patients with distant metastases at first admission all belonged to the low count group. These results suggest that the number of mast cells within and around the tumor is a useful prognostic factor for STS.
Human herpesvirus 6 (HHV‐6) was isolated from patients with exanthem subitum (ES) with a high frequency, and it is now believed that this virus causes ES as a primary infection in childhood. HHV‐6 infection is highly prevalent in early childhood and this virus may infect infants through the saliva mainly from mother to child. HHV‐6 has a tropism to CD4+ cells and destroys cells in vitro. Although children recover from ES without any sequelae, neurological symptoms associated with exanthem subitum are often observed, and we could detect HHV‐6 in the cerebrospinal fluid of ES patients. This result suggests that HHV‐6 may invade the central nervous system and cause neurological symptoms.
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