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Long-term potentiation in pyramidal outputs of supragranural layers of the rat auditory cortex
s210 LONG-TERM POTENTIATION IN PYRAMIDAL OUTPUTS OF SUPRAGRANURAL LAYERS OF KI, Dent. of < K THE RAT AUDITORY CORTEX. N euroDhvslo‘1 , Br'ain Res. Inst. Niiaata Univ. 1 Asah i-machi Nii aata 95 1 , JaDa n
1803
is elicited in field potentials We have found that long-term potentiation (LTP) recorded from layers II/III after tetanic stimulation of white matter in auditory This LTP seems to correspond to increase of orthodromic cortex slices of adult rats. In this study, we conducted morphological firing in pyramidal neurons. identification of neurons recorded from layers II/III using injection of biocytin Most through patch electrode and labeling it with avidin-fluorescent dye conjugate. of units which responded to white matter stimulation with antidromic spikes were identical as pyramidal neurons of which somata were in layers II/III. We also investigated LTP in firing probability of these neurons following white matter Firing probability of stimulation by recording unit activities extracellularly. was maintained orthodromic spikes was potentiated after tetani and this potentiation as well as that in field for 30 min, at least. This LTP in the firing probability, indicating these changes were evoked by potentials, was blocked by D-APV(SOpM), These results suggest that the LTP in field potentials activation of NMDA receptors. and that LTP to potentiation of firing probability of pyramidal outputs corresponds in the auditory cortex evokes dynamic changes of the input-output relationship in neural networks.
1804
VISUALIZATION OF AUDITORY CORTICAL ACTIVITY OF GUINEA PIG BY OPTICAL RECORDING WITH CCD CAMERA. TORU HASHIMOTO, Inst. Med. & Dent. Enain.. Tokvo Med. & Dent. Univ.. Tokyo. 101. Japan.
The population activities of the auditory cortex of the guinea pig in response to species-specific vocalization were mapped. A “cooled CCD” camera was used to image the epi-fluorescence of a voltage-sensitive dye(RH795) applied to the cortical surface of animals, which were lightly anesthetized with Nembutal. The fluorescent images were sampled through pulsed illumination by a Xenon Lamp. The images of the responses were accumulated on the electric charge pattern over the CCD of the video camera and the background fluorescence was subtracted from the images to visualize the specific cortical activity in response to the sound stimulus. The spatio-temporal patterns of the auditory cortical activities were surveyed by a train of stroboscopically sampled images. The optical records showed spots, stripes or small island-like domains, which were temporally shifted over the auditory cortical areas. The global functional structure of the auditory cortex would be elucidated by the time series analysis of the optical records. The cortical representation of the animal’s vocalized sound would be a simple model of neuronal speech processing in the brain.
NEURONS IN THE PRIMARY AUDJTORY CORTEX ARE SENSITIVE TO SPECIFIC TEMPORAL PATTERNS: time Interval between frequencies and presentation order. Japaa kUPmHIRIQUIMAROUX. FRP.lost.ofl-91. 1805
The present study has examined whether neurons in the primary auditory cortex (Al) of the Japanese monkeys (Macacahcata) respond to temporal patterns of sound in order to understand the temporal information processing in the auditory system. A chamber was placed for chronic recordings over the left temporal lobe. The acoustic stimuli used were tone bursts and temporally paired tone bursts of different frequencies, which were monaurally presented (rise/fall time = 10 ms, plateau = 20 ms). Frequency, intensity and the interval between paired bursts (At) were variid. Unit recordings were made from Al contralateral to the stimulated ear. During recording sessions, the animal was anesthetized with a mixture of nitrous oxide and oxygen, supplemented by isoflurane. PST (post-stimulustime) histograms with 360 ms time window were analyzed. Results demonstrated that single neurons in Al often responded to different frequencies with totally diierent temporal firing patterns when the stimulus intensity was relatively high (60-70 dB SPL). On the contrary, they could not generate action potentials when the intensity got low, except for the best frequency of the neuron. However, these neurons facilitatively responded to a temporally paired tone bursts of dierent frequencies separated by a particular At even when the intensity of each frequency was low. The At which elicited the facilitation ranged from -50 ms to -200 ms under conditions used in this study (e.g., 2 kHz and 1 kHz with At = 160 ms; 600 Hz and 6 kHz with At = 90 ms). The tuning to At was broad and the neurons dii not show facilitative responses to temporal pairs with reversed order. Thus, these neurons appear to be sensitive to a combination of frequencies, At and the order of presentatrion. The best frequency, which produces the shortest latency, had to be placed last in the temporal combination to produce a facilitation. The data indicate that Al neurons encode temporal patterns of sound.
1803
is elicited in field potentials We have found that long-term potentiation (LTP) recorded from layers II/III after tetanic stimulation of white matter in auditory This LTP seems to correspond to increase of orthodromic cortex slices of adult rats. In this study, we conducted morphological firing in pyramidal neurons. identification of neurons recorded from layers II/III using injection of biocytin Most through patch electrode and labeling it with avidin-fluorescent dye conjugate. of units which responded to white matter stimulation with antidromic spikes were identical as pyramidal neurons of which somata were in layers II/III. We also investigated LTP in firing probability of these neurons following white matter Firing probability of stimulation by recording unit activities extracellularly. was maintained orthodromic spikes was potentiated after tetani and this potentiation as well as that in field for 30 min, at least. This LTP in the firing probability, indicating these changes were evoked by potentials, was blocked by D-APV(SOpM), These results suggest that the LTP in field potentials activation of NMDA receptors. and that LTP to potentiation of firing probability of pyramidal outputs corresponds in the auditory cortex evokes dynamic changes of the input-output relationship in neural networks.
1804
VISUALIZATION OF AUDITORY CORTICAL ACTIVITY OF GUINEA PIG BY OPTICAL RECORDING WITH CCD CAMERA. TORU HASHIMOTO, Inst. Med. & Dent. Enain.. Tokvo Med. & Dent. Univ.. Tokyo. 101. Japan.
The population activities of the auditory cortex of the guinea pig in response to species-specific vocalization were mapped. A “cooled CCD” camera was used to image the epi-fluorescence of a voltage-sensitive dye(RH795) applied to the cortical surface of animals, which were lightly anesthetized with Nembutal. The fluorescent images were sampled through pulsed illumination by a Xenon Lamp. The images of the responses were accumulated on the electric charge pattern over the CCD of the video camera and the background fluorescence was subtracted from the images to visualize the specific cortical activity in response to the sound stimulus. The spatio-temporal patterns of the auditory cortical activities were surveyed by a train of stroboscopically sampled images. The optical records showed spots, stripes or small island-like domains, which were temporally shifted over the auditory cortical areas. The global functional structure of the auditory cortex would be elucidated by the time series analysis of the optical records. The cortical representation of the animal’s vocalized sound would be a simple model of neuronal speech processing in the brain.
NEURONS IN THE PRIMARY AUDJTORY CORTEX ARE SENSITIVE TO SPECIFIC TEMPORAL PATTERNS: time Interval between frequencies and presentation order. Japaa kUPmHIRIQUIMAROUX. FRP.lost.ofl-91. 1805
The present study has examined whether neurons in the primary auditory cortex (Al) of the Japanese monkeys (Macacahcata) respond to temporal patterns of sound in order to understand the temporal information processing in the auditory system. A chamber was placed for chronic recordings over the left temporal lobe. The acoustic stimuli used were tone bursts and temporally paired tone bursts of different frequencies, which were monaurally presented (rise/fall time = 10 ms, plateau = 20 ms). Frequency, intensity and the interval between paired bursts (At) were variid. Unit recordings were made from Al contralateral to the stimulated ear. During recording sessions, the animal was anesthetized with a mixture of nitrous oxide and oxygen, supplemented by isoflurane. PST (post-stimulustime) histograms with 360 ms time window were analyzed. Results demonstrated that single neurons in Al often responded to different frequencies with totally diierent temporal firing patterns when the stimulus intensity was relatively high (60-70 dB SPL). On the contrary, they could not generate action potentials when the intensity got low, except for the best frequency of the neuron. However, these neurons facilitatively responded to a temporally paired tone bursts of dierent frequencies separated by a particular At even when the intensity of each frequency was low. The At which elicited the facilitation ranged from -50 ms to -200 ms under conditions used in this study (e.g., 2 kHz and 1 kHz with At = 160 ms; 600 Hz and 6 kHz with At = 90 ms). The tuning to At was broad and the neurons dii not show facilitative responses to temporal pairs with reversed order. Thus, these neurons appear to be sensitive to a combination of frequencies, At and the order of presentatrion. The best frequency, which produces the shortest latency, had to be placed last in the temporal combination to produce a facilitation. The data indicate that Al neurons encode temporal patterns of sound.