Transmission Of Neural Activity Research Articles

Alpha-band cortico-cortical phase synchronization is associated with effective connectivity in the motor network

ObjectiveCommunication-through-coherence proposes that the phase synchronization (PS) of neural oscillations between cortical areas supports neural communication. In this study, we exploited transcranial magnetic stimulation (TMS)-evoked potentials (TEPs) to test this hypothesis at the macroscale level, i.e., whether PS between cortical areas supports interarea communication. TEPs are electroencephalographic (EEG) responses time-locked to TMS pulses reflecting interarea communication, as they are generated by the transmission of neural activity from the stimulated area to connected regions. If interarea PS is important for communication, it should be associated with the TEP amplitude in the connected areas. MethodsTMS was delivered over the left primary motor cortex (M1) of fourteen healthy volunteers, and 70-channel EEG was recorded. Early TEP components were source-localized to identify their generators, i.e., distant brain regions activated by M1 through effective connections. Next, linear regressions were used to test the relationship between the TEP amplitude and the pre-stimulus PS between the M1 and the connected regions in four frequency bands (range 4–45 Hz). ResultsPre-stimulus interarea PS in the alpha-band was positively associated with the amplitude of early TEP components, namely, the N15 (ipsilateral supplementary motor area), P25 (contralateral M1) and P60 (ipsilateral parietal cortex). ConclusionsAlpha-band PS predicts the response amplitude of the distant brain regions effectively connected to M1. SignificanceOur study supports the role of EEG-PS in interarea communication, as theorized by communication-through-coherence.

Transmission of neural activity in a feedforward network

In this work, the enhancement of coherence resonance of firings in a 10-layer feedforward neuronal network with sparse couplings is found when there is noise input to each layer. Periodic signals with frequency 30-80 Hz are found to be well transmitted though the network, and such a frequency sensitivity can be modulated by the noise intensity and is different in different layers. When a random pulse-like signal is input to the neurons of the first layer, the signal can be well read out from the population rates in an optimal range of noise intensity. This ability decreases as the layer index increases.

The Role of the Temporal Lobe in Feline Aggression and Defense

Four lines of research are reviewed which investigated the role of the amygdala, ventromedial hypothalamus, bed nucleus of the stria terminalis, ventral hippocampus and the benzodiazepine receptor in predatory aggression and defense in the cat. The first two lines of research involved permanently increasing defensive response to threat either by repeatedly inducing subclinical seizure discharges in the ventral hippocampus and amygdala or by administering the benzodiazepine inverse agonist, anxiogenic compound FG-7142. In the third line of research, defensive response of cats was both transiently and lastingly reduced by high frequency stimulation of the basolateral amygdala. The fourth line of research examined the relationship between spontaneous cellular response to species-characteristic threat and individual differences in transmission of neural activity between the amygdala and ventromedial hypothalamus. Together, these studies point to the importance of the amygdalo-ventromedial hypothalamic pathway in defensive response to some, but not all conspecific threats. They also implicate other limbic pathways in the suppression of predatory aggressive responses. The amygdalo-bed nucleus of the stria terminalis pathway does not appear to be important in mediating defensive response to prey, but it is implicated in suppression of some types of predatory aggression. Neural inhibition and facilitation in particular cell fields of the ventral hippocampus seem to play a role in modulation of predatory aggression. Finally, the benzodiazepine receptor may be involved in modulating excitability in the amygdalo-VMH pathway, and it may also participate in a separate neural substrate which suppresses approach-attack behaviors.

Effects of insulin injection on responses of olfactory bulb and amygdala single units to odors

The effect of insulin injection on transmission of neural activity within the olfactory system of the anesthetized male rat was investigated at the single unit level. It was found that insulin changed the response to odors of approximately 27% of olfactory bulb units and 21% of amygdala units tested. Many of the changes were in the direction of an increase in response magnitude, but there were some reversals in response direction and other complex changes. There was no evidence of a selective facilitation of responses to food odor as compared to non-food odors. Control observations of the response of thalamic somatosensory units to tactual stimulation showed no effects of insulin. These results suggest that hypothalamic hunger mechanisms may normally interact with olfactory mechanisms to augment and otherwise change the response of some olfactory system units to various odors.