Waves Of Neuronal Activity Research Articles

Divergent neuronal activity patterns in the avian hippocampus and nidopallium.

Sleep-related brain activity occurring during non-rapid eye-movement (NREM) sleep is proposed to play a role in processing information acquired during wakefulness. During mammalian NREM sleep, the transfer of information from the hippocampus to the neocortex is thought to be mediated by neocortical slow-waves and their interaction with thalamocortical spindles and hippocampal sharp-wave ripples (SWRs). In birds, brain regions composed of pallial neurons homologous to neocortical (pallial) neurons also generate slow-waves during NREM sleep, but little is known about sleep-related activity in the hippocampus and its possible relationship to activity in other pallial regions. We recorded local field potentials (LFP) and analogue multiunit activity (AMUA) using a 64-channel silicon multi-electrode probe simultaneously inserted into the hippocampus and medial part of the nidopallium (i.e., caudal medial nidopallium; NCM) or separately into the caudolateral nidopallium (NCL) of adult female zebra finches (Taeniopygia guttata) anesthetized with isoflurane, an anesthetic known to induce NREM sleep-like slow-waves. We show that slow-waves in NCM and NCL propagate as waves of neuronal activity. In contrast, the hippocampus does not show slow-waves, nor sharp-wave ripples, but instead displays localized gamma activity. In conclusion, neuronal activity in the avian hippocampus differs from that described in mammals during NREM sleep, suggesting that hippocampal memories are processed differently during sleep in birds and mammals.

A Switch and Wave of Neuronal Activity in the Cerebral Cortex During the First Second of Conscious Perception.

Conscious perception occurs within less than 1 s. To study events on this time scale we used direct electrical recordings from the human cerebral cortex during a conscious visual perception task. Faces were presented at individually titrated visual threshold for 9 subjects while measuring broadband 40-115 Hz gamma power in a total of 1621 intracranial electrodes widely distributed in both hemispheres. Surface maps and k-means clustering analysis showed initial activation of visual cortex for both perceived and non-perceived stimuli. However, only stimuli reported as perceived then elicited a forward-sweeping wave of activity throughout the cerebral cortex accompanied by large-scale network switching. Specifically, a monophasic wave of broadband gamma activation moves through bilateral association cortex at a rate of approximately 150 mm/s and eventually reenters visual cortex for perceived but not for non-perceived stimuli. Meanwhile, the default mode network and the initial visual cortex and higher association cortex networks are switched off for the duration of conscious stimulus processing. Based on these findings, we propose a new "switch-and-wave" model for the processing of consciously perceived stimuli. These findings are important for understanding normal conscious perception and may also shed light on its vulnerability to disruption by brain disorders.

Neuronal chains as processing units of long scale wave information

Information processing in the brain relies on the functional cooperation of individual neurons and neuronal nuclei. It is widely accepted that such cooperation may occur in time domain through synchronous firing of multiple, including spatially distant, neurons. Complementary, the brain, as spatially extended complex structure, may also employ coding and processing of long-scale information in spatial dimension. This alternative, significantly less explored in the literature, recently received experimental support. Here we propose a novel concept of spatiotemporal representation and processing of long-scale information in laminar neural structures. According to this idea, relevant information may be coded in self-sustained traveling waves of neuronal activity whose nonlinear interaction yields efficient wave-processing of spatiotemporal information. We study this concept by modeling the spatially extended neural activity in a chain of FitzHugh-Nagumo neurons with an additional voltage-gated membrane current. This local mechanism turns nonlinear traveling waves in a carrier of long-scale information. Long scale waves can interact between one another, which may lead to complete or asymmetric annihilation and transparent crossing. Then the wave interaction can selectively change information contained in the neuronal structure. We show that laminar neuronal structures exhibit a variety of functionally different regimes including, e.g., decimation of the input stimuli. Moreover they can selectively compress stimuli in the natural frequency range and process them differently by considering the context in which they appear, i.e. other waves involved in the processing. Thus neuronal chains can work as processing units performing different operations over spatiotemporal information.

Vibration Isolation Critical to Measuring Neuronal Patterns in the Brain

Abstract Researchers at Georgetown University's Department of Physiology and Biophysics use negative-stiffness vibration isolators to help measure micron-level patterns of neuronal activity in the mammalian neocortex. The research is shedding new light into brain sensory and motor processing functions relating to cardiac fibrillation and epilepsy. Isolating a laboratory's sensitive microscopy equipment against low-frequency vibration has become increasingly more vital to maintaining imaging quality and data integrity for neurobiology researches. Ever more frequently, laboratory researchers are discovering that conventional air tables and the more recent active (electronic) vibration isolation systems are not able to adequately cancel out the lower frequency perturbations derived from air conditioning systems, outside vehicular movements and ambulatory personnel. Such was the case with the Department of Physiology and Biophysics at Georgetown University Medical Center, where Professor Jian-Young Wu has been conducting research on waves of neuronal activity in the neocortex of the brain.

Involvement of the σ Receptor inPassive-Avoidance Learning in the Day-Old Chick during the Second Wave of Neuronal Activity

The specific σ-receptor agonist (+)-SKF 10047 and antagonist BD 1047 were used to investigate whether this receptor was involved in passive-avoidance training in the day-old chick. We found 300 μM (+)-SKF 10047 to be amnesic when injected into the lobus parolfactorius 5 h after training (p < .01). Higher or lower concentrations of (+)-SKF 10047 did not disrupt memory formation. The amnesia produced by the efficacious dose of (+)-SKF 10047 was reversed by the specific antagonist, BD 1047. It is suggested that the σ-receptor may exert its effect on passive-avoidance memory consolidation during the later stages of long-term memory formation by modulation of memory-related neurotransmission.

Identification of the opioid receptors involved in passive-avoidance learning in the day-old chick during the second wave of neuronal activity

Long-term memory formation for passive-avoidance learning in the day-old chick is known to have two distinct time windows of protein synthesis (F.M. Freeman, S.P.R. Rose, A.B. Scholey, 1995. Two time windows of anisomycin-induced amnesia for passive-avoidance training in the day-old chick. Neurobiol. Learn. Mem. 63, 291–295). The lobus parolfactorius (LPO) is thought to be an important site for the second wave of protein synthesis which occurs 4–5 h after training. Birds received bilateral intracranial injections of agonists and antagonists for the μ-, δ-, κ-opioid receptors and the opioid receptor-like (ORL 1) receptor directly into the LPO at 5 h post-training and were tested for recall 24 h later. Also, 100 μM β-funaltrexamine (β-FAN), a μ-opioid receptor antagonist, significantly impaired memory formation ( P<0.01). The δ-opioid receptor was also involved in memory formation at this time-point since antagonism of this receptor by 1 mM ICI-174,864 caused amnesia ( P<0.01) which was reversed by the agonist, DPLPE. The κ-opioid receptor appeared not to be involved during the second phase of neuronal activity since neither stimulation by dynorphin nor inhibition by nor-BIN caused amnesia for the task. The ORL 1 receptor agonist orphanin FQ also had no effect suggesting that this receptor was not involved at this 5-h time-point. Cytosolic and mitochondrial protein synthesis has been shown to be important in passive-avoidance learning in the day-old chick. Both chloramphenicol (CAP) and anisomycin (ANI), inhibitors of mitochondrial and cytosolic protein synthesis, respectively, caused disruption when injected 5 h post-training into the LPO ( P<0.05). Endomorphin-2 (Endo-2), a μ-opioid receptor agonist, reversed both the ANI- and CAP-sensitivity. However, DPLPE, a δ-opioid receptor agonist, only reversed the effect due to CAP. Possible mechanisms for these effects are discussed.