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• We first provide the direct intracranial evidence in the human brain that supports the framework of phenomenon and access consciousness. • We further characterize the spatiotemporal dynamics and the relationship of the two different NCCs more precisely. • Our results show that lateral PFC may be a key node linking phenomenon and access consciousness. After more than 30 years of extensive investigation, impressive progress has been made in identifying the neural correlates of consciousness (NCC). However, the functional role of spatiotemporally distinct consciousness-related neural activity in conscious perception is debated. An influential framework proposed that consciousness-related neural activities could be dissociated into two distinct processes: phenomenal and access consciousness. However, though hotly debated, its authenticity has not been examined in a single paradigm with more informative intracranial recordings. In the present study, we employed a visual awareness task and recorded the local field potential (LFP) of patients with electrodes implanted in cortical and subcortical regions. Overall, we found that the latency of visual awareness-related activity exhibited a bimodal distribution, and the recording sites with short and long latencies were largely separated in location, except in the lateral prefrontal cortex (lPFC). The mixture of short and long latencies in the lPFC indicates that it plays a critical role in linking phenomenal and access consciousness. However, the division between the two is not as simple as the central sulcus, as proposed previously. Moreover, in 4 patients with electrodes implanted in the bilateral prefrontal cortex, early awareness-related activity was confined to the contralateral side, while late awareness-related activity appeared on both sides. Finally, Granger causality analysis showed that awareness-related information flowed from the early sites to the late sites. These results provide the first LFP evidence of neural correlates of phenomenal and access consciousness, which sheds light on the spatiotemporal dynamics of NCC in the human brain. [ABSTRACT FROM AUTHOR]

Sensorimotor beta oscillations are increased in Parkinson's disease (PD) due to the alteration of dopaminergic transmission. This electrophysiological read-out is reported both in patients and in animal models such as the 6-OHDA rat model obtained with unilateral nigral injection of 6-hydroxydopamine (6-OHDA). Current treatments, based on dopaminergic replacement, transiently normalize this pathological beta activity and improve patients' quality of life. We wanted to assess in vivo whether the abnormal beta oscillations can be correlated with impaired striatal or cortical excitability of the sensorimotor system and modulated by the pharmacological manipulation of the dopaminergic system. In the unilateral 6-OHDA rat model and control animals, we used intra-striatal and intra-cortical single-pulse electrical stimulation (SPES) and concurrent local field potentials (LFP) recordings. In the two groups, we quantified basal cortico-striatal excitability from time-resolved spectral analyses of LFP evoked responses induced remotely by intracerebral stimulations. The temporal dependance of cortico-striatal excitability to dopaminergic transmission was further tested using electrophysiological recordings combined with levodopa injection. LFP evoked responses after striatal stimulation showed a transient reduction of power in a large time-frequency domain in the 6-OHDA group compared to the sham group. This result was specific to the striatum, as no significant difference was observed in cortical LFP evoked responses between the two groups. This impaired striatal excitability in the 6-OHDA group was observed in the striatum at least during the first 3 months after the initial lesion. In addition, the striatum responses to SPES during a levodopa challenge showed a transient potentiation of the decrease of responsiveness in frequencies below 40 Hz. The spectral properties of striatal responses to SPES show high sensitivity to dopaminergic transmission in the unilateral 6-OHDA rat model. We thus propose that this approach could be used in preclinical models as a time-resolved biomarker of impaired dopaminergic transmission capable of monitoring progressive neurodegeneration and/or challenges to drug intake. • Electrical stimulation shows decreased striatal excitability in 6-OHDA animals. • This effect is stable at least during the first 3 months after 6-OHDA lesion. • Levodopa challenges modulate responses to electrical stimulation. [ABSTRACT FROM AUTHOR]

We review a simple yet versatile approach for the analysis of multichannel data, focusing in particular on brain signals measured with EEG, MEG, ECoG, LFP or optical imaging. Sensors are combined linearly with weights that are chosen to provide optimal signal-to-noise ratio. Signal and noise can be variably defined to match the specific need, e.g. reproducibility over trials, frequency content, or differences between stimulus conditions. We demonstrate how the method can be used to remove power line or cardiac interference, enhance stimulus-evoked or stimulus-induced activity, isolate narrow-band cortical activity, and so on. The approach involves decorrelating both the original and filtered data by joint diagonalization of their covariance matrices. We trace its origins; offer an easy-to-understand explanation; review a range of applications; and chart failure scenarios that might lead to misleading results, in particular due to overfitting. In addition to its flexibility and effectiveness, a major appeal of the method is that it is easy to understand. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Oscillatory activity in the beta band is increased in the subthalamic nucleus (STN) of Parkinson's disease (PD) patients. Rigidity and bradykinesia are associated with the low-beta component (13–20Hz) but the neurophysiological correlate of freezing of gait in PD has not been ascertained. Methods: We evaluated the power and coherence of the low- and high-beta bands in the STN and cortex (EEG) of PD patients with (p-FOG) (n=14) or without freezing of gait (n-FOG) (n=8) in whom electrodes for chronic stimulation in the STN had been implanted for treatment with deep brain stimulation. Results: p-FOG patients showed higher power in the high-beta band (F=11.6, p=0.002) that was significantly reduced after l-dopa administration along with suppression of FOG (F=4.6, p=0.042). High-beta cortico-STN coherence was maximal for midline cortical EEG electrodes, whereas the low-beta band was maximal for lateral electrodes (χ 2 =20.60, p<0.0001). Conclusions: The association between freezing of gait, high-beta STN oscillations and cortico-STN coherence suggests that this oscillatory activity might interfere in the frontal cortex–basal ganglia networks, thereby participating in the pathophysiology of FOG in PD. [Copyright &y& Elsevier]

Highlights: [•] An approach to record local field potentials of taste epithelium in umami stimuli. [•] By multichannel recording, the temporal characteristics of signals were analyzed. [•] A dose-dependent behavior in increasing concentrations of umami was detected. [•] A synergistic enhancement between amino acids and nucleotides can be detected. [•] The study provides a promising approach to distinguish and evaluate umami tastants. [ABSTRACT FROM AUTHOR]

Abstract: Intracerebral recordings of neuronal activity in patients undergoing deep brain stimulation have revealed characteristic movement-related desynchronization at frequencies <30Hz and increased activity in the gamma band (~30–100Hz) in the basal ganglia and thalamus. Thalamic gamma activity is also found during arousal. Here, we explore oscillatory gamma band activity recorded from the ventralis intermedius nucleus of the thalamus during motor performance in a Go/noGo task in 10 patients with essential tremor after implantation of deep brain stimulation electrodes. We show that movement-related gamma activity is lateralized to the nucleus contralateral to the moved side similar to previous findings in the globus pallidus internus and the subthalamic nucleus. The onset of contralateral gamma band synchronization following imperative Go cues is positively correlated with reaction time. Remarkably, baseline levels of gamma activity shortly before the Go cue correlated with the reaction times. Here, faster responses occurred in patients with higher levels of pre-cue gamma activity. Our findings support the role of gamma activity as a physiological prokinetic activity in the motor system. Moreover, we suggest that subtle fluctuations in pre-cue gamma band activity may have an impact on task performance and may index arousal-related states. [Copyright &y& Elsevier]

Abstract: In the normal brain beta band oscillatory activity has been associated with retaining of ongoing motor activities. In Parkinson's disease, enhanced beta band oscillatory activity is displayed across the cortico-basal ganglia pathway and is one of the prominent neurophysiological phenomena associated with the disorder. Intraoperative and postoperative recordings of neural activity in patients undergoing stereotactic neurosurgery combined with studies in animal models of parkinsonism have led to the accumulation of complementary data regarding these oscillations. In this review we address some of the key issues facing researchers in the field. These issues encompass existing agreements as well as open debates in modern studies of beta band oscillations, including their defining characteristics, links to clinical symptoms and the functional properties of their formation and effects on behavior. We address these questions by comparing and contrasting the results of neurophysiological observations in human patients, MPTP primate model and 6-OHDA rat model with conceptual and computational models of the normal and parkinsonian basal ganglia. Defining a unifying scheme of beta band oscillations and their relation to neurophysiological, functional and clinical phenomena will enable future targeting of these oscillations for both diagnosis and treatment of Parkinson's disease. [Copyright &y& Elsevier]