Cortical reorganization following anterior temporal lobectomy in patients with temporal lobe epilepsy.

BACKGROUND: Functional MRI was used to study the impact of temporal lobe epilepsy (TLE) and anterior temporal lobectomy (ATL) on the cortical language network in patients with medically refractory TLE. METHODS: Nineteen patients with medically refractory TLE and 11 healthy control subjects were enrolled in this study. Ten patients underwent left ATL (mean age 35.2 +/- 3.8 years), and 9 underwent right ATL (mean age 35.9 +/- 2.6 years). The subjects silently generated verbs in response to a series of visually presented nouns inside the scanner. Correlation analysis was performed between the subjects' performance on the clinical language tests and their neural response in the a priori cortical regions. RESULTS: Preoperative data revealed that the patients with TLE showed increased neural activity in the right inferior frontal gyri (IFG) and middle frontal gyri (MFG). The right TLE patients demonstrated strong correlation between their language performance and the level of cortical activation within the typical language areas. However, such a correlation was absent in the left TLE patients. After the ATL surgery, the left TLE patients showed reduced activation in the left MFG and right IFG, whereas no difference was observed in the right TLE patients. In the right TLE patients, the correlation between language performance and neural response shifted from the typical language areas to the anterior cingulate cortex. CONCLUSION: This study demonstrates that the cortical language network is affected differently by the left and right temporal lobe epilepsy and is reorganized after anterior temporal lobectomy.

Analysis of 22 kHz ultrasonic vocalization in laboratory rats: long and short calls.

There is a remarkable variation in the length of single ultrasonic calls emitted by adult rats. The duration of calls is likely to convey information for conspecifics. The goal of the present study was to analyze 22 kHz calls emitted by naive laboratory rats in response to contact with the human hand and to measure their acoustic features, with a particular emphasis on call duration. Repeated hand touch applied to the nape of the neck of rats induced ultrasonic calls, 97.4% of which were within the range of 20-29 kHz and 2.6% of which were within 44-67 kHz. Distribution of duration of 6765 calls revealed two subpopulations of 22 kHz calls: 20-300 ms calls with its peak at 150 ms and calls above 310 ms with highest values at approximately 500-600 ms without a clear peak. These two call populations were referred to as short and long calls, respectively. The short and the long vocalizations contained 80% and 100% of calls within the range of the 22 kHz frequency, respectively. The findings indicated that, in the situation studied, the 22 kHz vocalization of adult rats consists of two distinguishable subpopulation of calls: short and long with the boundary between them at 300 ms.

Comparison between cholinergically and naturally induced ultrasonic vocalization in the rat.

Ultrasonic vocalization in rats accompanying stressful situations or induced by direct brain stimulation may be used as a measure of emotionality and as a potential response model for testing anti-anxiety agents. The aim of the present study was to compare physical features of pharmacologically-induced ultrasonic vocalization with naturally triggered vocalization. Ultrasonic calls induced by hand touch, footshock, or by direct intracerebral injection of carbachol in adult rats were compared. Ultrasonic calls obtained in all these situations were described as '22 kHz' vocalization. Average frequencies of vocalization were 24.1 +/- 0.78 kHz, 26.0 +/- 2.64 kHz and 25.0 +/- 1.87 (SD) kHz for handled, footshocked and carbachol injected rats, respectively, and they did not differ significantly from each other. Histograms of single call duration showed similar distribution patterns for all groups with a predominance of long calls, although carbachol-induced calls were shorter than calls induced by touch or footshock. Histograms for inter-call intervals showed one major peak at 100-150 ms for all groups. Sonograms and power spectra showed similar characteristics both for calls induced by intracerebral carbachol and by hand touch or footshock. The results indicate that physical features of ultrasonic vocalization induced by intracerebral carbachol are comparable with those for naturally induced vocalization and fall into the category of '22 kHz' calls.

Response of neurons of the rat anterior hypothalamic-preoptic area to carbachol.

Behavioural effects of carbachol given into the hypothalamic/preoptic area have been demonstrated but there is a paucity of information about the response of single neurons to carbachol. The aim of the present study was to determine the response of spontaneously firing neurons in the rat hypothalamic/preoptic area to application of carbachol by iontophoresis or by pressure injection in a dose and volume comparable with that used in behavioural studies. Extracellular single unit recordings showed a significant decrease in mean firing rate in 82% of neurons responding to iontophoretic carbachol and in 75.5% of neurons responding to carbachol injected about 600 microns away. An increase in firing rate occurred in only 15 and 17.6% of neurons, respectively. Application of saline did not alter the mean firing rate while application of glutamate into the same areas or ejection into the vicinity of the same neurons caused an increase in mean firing rate in 94% of responding neurons. The results indicate that a decrease in mean firing rate is the predominant neuronal response to carbachol in the anteromedial hypothalamic/preoptic area of the rat and we suggest that this decrease may be associated with behavioural responses to carbachol.

Secondary generalization of seizures from a cortical penicillin focus following stimulation of the basal forebrain.

The basal forebrain has been implicated in the regulation of generalized motor convulsive activity particularly from amygdala kindling. The effect of electrical stimulation of the substantia innominata and ventral pallidal regions of the basal forebrain in rats with acute interictal penicillin foci in the frontal parietal neocortex was determined. Stimulation of this area resulted in generalized cortical EEG synchronization, an inconsistent effect on interictal spike frequency, and generalized seizures that were not prevented by atropine. The results support a role for these basal forebrain structures in the regulation of generalized seizures from a cortical focus mediated primarily through influences on thalamocortical pathways.

Ultrasonic vocalization in rats produced by cholinergic stimulation of the brain.

Neurotransmitters involved in production of ultrasounds in rodents have not yet been identified. It is also not known whether brain mechanisms regulating production of ultrasounds and audible sounds are similar or different. The present study provides the first report that intracerebral injection of an acetylcholine agonist, carbachol, in rats induces ultrasonic vocalization. Since the same agent can induce audible vocalization in cats, the finding suggests a possible common neurochemical substrate underlying production of sonic and ultrasonic vocalization in mammals. The data accumulated to date indicate also that these two kinds of vocalization may play a homologous role in animal communication.