Efficacy of Thalamocortical and Intracortical Synaptic Connections

Gil, Ziv; Connors, Barry W.; Amitai, Yael

doi:10.1016/s0896-6273(00)80788-6

Cited by 308 publications

(302 citation statements)

References 70 publications

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“…In general, synapses with a high probability of release display ftequency-dependent depression due ta a transient depletion in available neurotransmitter (Stevens & Wang, 1995). In fact, it bas been recendy demonstrated in a slice preparation that thalamocortical synapses have a greater probability of release, relative to intracortical~pses (Gil et al, 1999). The short-tenn dynamics of these two pathways correspond ta what would he expected given differences in release probability.…”

Section: The Decrementai Responsementioning

confidence: 85%

Input-specific effects of acetylcholine on sensory and intracortical evoked responses in the “barrel cortex” in vivo

2003

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Section: The Decrementai Responsementioning

confidence: 85%

Input-specific effects of acetylcholine on sensory and intracortical evoked responses in the “barrel cortex” in vivo

2003

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“…7a). Thalamocortical synapses are more effective than intracortical synapses 94 , but they form only a small fraction of the synapses onto SSCs 95,96 . Nevertheless, collectively they seem to be efficient in driving the SSCs 45,97 .…”

Section: Gated Temporal Information Transfer Between Cortical Layer 4mentioning

confidence: 99%

Regulation of spike timing in visual cortical circuits

2008

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A train of action potentials (a spike train) can carry information in both the average firing rate and the pattern of spikes in the train. But can such a spike-pattern code be supported by cortical circuits? Neurons in vitro produce a spike pattern in response to the injection of a fluctuating current. However, cortical neurons in vivo are modulated by local oscillatory neuronal activity and by top-down inputs. In a cortical circuit, precise spike patterns thus reflect the interaction between internally generated activity and sensory information encoded by input spike trains. We review the evidence for precise and reliable spike timing in the cortex and discuss its computational role.Reliability and precision are two different quantities. When you make an appointment with your friend, she can either keep the appointment or not show up at all. If she does show up, she might or might not be on time. The former uncertainty is related to reliability, whereas the latter is related to precision. When the same stimulus waveform is repeatedly injected at the soma of a neuron in vitro (FIG. 1a), a similar spike train is obtained on each trial 1,2 (FIG. 1b). When approximately the same number of spikes occur on each trial the neuron is said to be reliable, whereas when the spikes occur almost at the same time across trials it is said to be precise (FIG. 1c). For a single neuron, the potential information content of precise and reliable spike times is many times larger than that which is contained in the firing rate, which is averaged across a typical interval of a hundred milliseconds [3][4][5][6] . The information contained in spike timing is available immediately, rather than after an averaging period. Furthermore, the timing of patterns of spikes can potentially transmit even more information than the timing of the individual constituent spikes 3,7 . The potential relevance of spike patterns becomes apparent when we consider neurons at the population level: when a group of similar neurons (a 'pool') produces precise and reliable spike trains, the neurons they project to receive volleys of synchronous spikes 8,9 . This opens up the possibility of communicating between different cortical areas through synchronous spike volleys.In contrast to the in vitro situation described above, in the intact cortex most excitatory synaptic inputs arrive at the dendrites rather than at the soma (FIG. 1d), and synaptic transmission is typically unreliable [10][11][12][13] . Furthermore, most of these dendritic inputs are not directly related to ongoing sensory stimulation; rather, they reflect spatiotemporally structured internal activity. Therefore, when the same stimulus is presented repeatedly, the resulting spike trains are usually neither precise nor reliable when they are aligned to the stimulus onset 6 . Instead, HHMI Author ManuscriptHHMI Author Manuscript HHMI Author Manuscript neural activity in vivo might be dominated by internally generated complex reverberations or rhythmic oscillations, and precise and reliable sp...

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“…However, the responses we recorded receive a large contribution of local circuit activity from different sources (Tarczy-Hornoch et al, 1999;Martin, 2002;Schubert et al, 2003) making predictions about the electrotonic distribution of the input very difficult. The second mechanism is supported in part by the highly synchronized input from thalamus to layer 4 at the highest velocity (Pinto et al, 2000), which has a high efficacy (Gil et al, 1999). This input also reaches layer 6 and could help increase the dV/dt of IGr cells.…”

Section: Differences In Synaptic and Spike Responses From Different Lmentioning

confidence: 99%

Synaptic Responses to Whisker Deflections in Rat Barrel Cortex as a Function of Cortical Layer and Stimulus Intensity

Wilent¹,

Contreras²

2004

J. Neurosci.

126

115

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To study the synaptic and spike responses of barrel cortex neurons as a function of cortical layer and stimulus intensity, we recorded intracellularly in vivo from barbiturate anesthetized rats while increasing the velocity-acceleration of the whisker deflection. Granular (Gr; layer 4) cells had the EPSP with the shortest peak and onset latency, whereas supragranular (SGr; layers 2-3) cells had the EPSP with longest duration and slowest rate of rise. Infragranular (Igr; layers 5-6) cells had intermediate values, and thus each layer was unique. The spike response peak of Gr cells was followed by IGr and then by SGr cells. In all cells, depolarization reduced the duration and amplitude of the response, but only in Gr cells did it reveal an early IPSP that cut short the EPSP. This early IPSP was associated with a large decrease in input resistance and an apparent reversal potential below spike threshold; consequently, synaptic integration in Gr cells was limited to the initial 5-7 msec of the response. In contrast, in SGr and IGr cells, results suggest an overlap in time of the EPSP and IPSP, with a small drop in input resistance and an apparent reversal potential above spike threshold, facilitating input integration for up to 20 msec. Decreasing stimulus intensity (velocity-acceleration) reduced the amplitude and increased the peak latency of the response without altering its synaptic composition. We propose that layer 4 circuits are better suited to perform coincidence detection, whereas supra and infragranular circuits are better designed for input integration.

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Efficacy of Thalamocortical and Intracortical Synaptic Connections

Cited by 308 publications

References 70 publications

Input-specific effects of acetylcholine on sensory and intracortical evoked responses in the “barrel cortex” in vivo

Input-specific effects of acetylcholine on sensory and intracortical evoked responses in the “barrel cortex” in vivo

Regulation of spike timing in visual cortical circuits

Synaptic Responses to Whisker Deflections in Rat Barrel Cortex as a Function of Cortical Layer and Stimulus Intensity

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