Painful cutaneous laser stimuli induce event-related gamma-band activity in the lateral thalamus of humans

Abstract

Kim JH, Chien JH, Liu CC, Lenz FA. Painful cutaneous laser stimuli induce event-related gamma-band activity in the lateral thalamus of humans. J Neurophysiol 113: 1564 -1573, 2015. First published December 10, 2014 doi:10.1152/jn.00778.2014.-Although the thalamus is an important module in "pain networks," there are few studies of the effect of experimental pain upon thalamic oscillations. We have now examined the hypothesis that, during a series of painful cutaneous laser stimuli, thalamic signals will show stimulus-related gamma-band spectral activity, which is modulated by attention to vs. distraction from the painful stimulus. When the series of laser stimuli was presented, attention was focused by counting the laser stimuli (count laser task), while distraction was produced by counting backward (count back plus laser task). We have studied the effect of a cutaneous laser on thalamic local field potentials and EEG activity during awake procedures (deep brain stimulation implants) for the treatment of essential tremor. At different delays after the stimulus, three low gamma-(30 -50 Hz) and two high gamma-band (70 -90 Hz) activations were observed during the two tasks. Greater high-gamma activation was found during the count laser task for the earlier window, while greater high-gamma activation was found during the count back plus laser task for the later window. Thalamic signals were coherent with EEG signals in the beta band, which indicated significant synchrony. Thalamic cross-frequency coupling analysis indicated that the phase of the lower frequency activity (theta to beta) modulated the amplitude of the higher frequency activity (low and high gamma) more strongly during the count laser task than during the count back plus laser task. This modulation might result in multiplexed signals each encoding a different aspect of pain. attention; thalamus; gamma band oscillations; EEG; human; pain A BROAD RANGE OF EVIDENCE demonstrates the involvement of both the thalamus and the cortex in nociceptive processing (Apkarian et al. 2005;

Functional role of induced gamma oscillatory responses in processing noxious and innocuous sensory events in humans

“…In addition, one recent MEG study of brain resting-state shows that the phase of the alpha oscillation in the thalamus couples with cortical gamma amplitude in healthy humans (Roux et al, 2013). Therefore, the stronger TFRs in the gamma band induced by noxious laser in the SI and PS regions may be partly originated from the sensory regions of the thalamus via attention related thalamo-cortical networks (Guillery et al, 1998; Schmid et al, 2012; Harris, 2013; Kim et al, 2015a). Nevertheless, it is important to note that the contribution of SI to specific nociceptive processing, although certain, may be functionally very small, as indicated by the small proportion of direct spinothalamic afferents to S1 in primates (Gingold et al, 1991; Dum et al, 2009; Kenshalo et al, 1980).…”

Classification of EEG signals to identify variations in attention during motor task execution

“…The time-frequency features from the MRCP which were used for attention classification during motor task 3 execution, were statistically different. Time-frequency features were obtained from different band power and 4 different time blocks of EEG signals which have been used in previous studies on attention (Kim et al, 2015;5 Polomac et al, 2015). Better performance of tempo-spectral features is in line with previous studies that show that the type of the tasks plays a key role in functional brain connection.…”

Neural oscillations in antipsychotic-naïve patients with a first psychotic episode

“…Taken together, these findings support the notion that, in FEP, both hyper-and hypo-activations are present in frontal cortical areas. Alterations in the low frequencies have only been observed in few previous studies (Gschwandtner et al 2009;Kim et al 2015;Knyazeva et al 2008). One possible reason for this discrepancy is that in the present study only antipsychotic-naïve patients were included, whereas most previous investigations had studied patients under the influence of antipsychotics, which might have obfuscated the detection of these alterations (Centorrino et al 2014;Kikuchi et al 2007).…”