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Left hemispheric ? band cerebral oscillatory changes correlate with verbal memory.

ABSTRACT: Event-related synchronisation (ERS) and event-related desynchronisation (ERD) have been observed via magnetoencephalography (MEG) in the language-dominant hemisphere. However, the relationship between ERS/ERD and clinical language indices is unclear. Therefore, the present study evaluated brain activity utilising MEG during a verb generation task in 36 subjects and determined ERS/ERD power values in ?, ?, ?, low ? and high ? frequency bands. To measure clinical language indices, we adopted Wechsler Memory Scale-revised. We observed ERD in the ? band from the bilateral occipital to the left central brain region, in the ? band from the bilateral occipital to the left frontal region and in the low ? band a high-power signal in the left frontal region. We also observed ERS in the ? band in bilateral frontal region and in the high ? band in bilateral occipital region. Furthermore, we found a significant negative correlation between ?-band ERD power at the left postcentral gyrus and medial superior frontal gyrus and verbal memory score (correlation coefficients?=??-?0.574 and -?0.597, respectively). These results suggest that individuals with lower linguistic memory have less desynchronised ?-band ERD power and ?-band ERD power in the left hemisphere may be a neurophysiological biomarker for verbal memory.

SUBMITTER: Araki T

PROVIDER: S-EPMC7490359 | biostudies-literature | 2020 Sep

REPOSITORIES: biostudies-literature

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Left hemispheric α band cerebral oscillatory changes correlate with verbal memory.

Araki Toshihiko T Watanabe Yoshiyuki Y Hirata Masayuki M

Scientific reports 20200914 1

Event-related synchronisation (ERS) and event-related desynchronisation (ERD) have been observed via magnetoencephalography (MEG) in the language-dominant hemisphere. However, the relationship between ERS/ERD and clinical language indices is unclear. Therefore, the present study evaluated brain activity utilising MEG during a verb generation task in 36 subjects and determined ERS/ERD power values in θ, α, β, low γ and high γ frequency bands. To measure clinical language indices, we adopted Wechs ...[more]

PMID: 32929146

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Project description:RationaleHigh frequency oscillations (HFO; ripples = 80-200, fast ripples 200-500 Hz) are promising epileptic biomarkers in patients with epilepsy. However, especially in temporal epilepsies differentiation of epileptic and physiological HFO activity still remains a challenge. Physiological sleep-spindle-ripple formations are known to play a role in slow-wave-sleep memory consolidation. This study aimed to find out if higher rates of mesial-temporal spindle-ripples correlate with good memory performance in epilepsy patients and if surgical removal of spindle-ripple-generating brain tissue correlates with a decline in memory performance. In contrast, we hypothesized that higher rates of overall ripples or ripples associated with interictal epileptic spikes correlate with poor memory performance.MethodsPatients with epilepsy implanted with electrodes in mesial-temporal structures, neuropsychological memory testing and subsequent epilepsy surgery were included. Ripples and epileptic spikes were automatically detected in intracranial EEG and sleep-spindles in scalp EEG. The coupling of ripples to spindles was automatically analyzed. Mesial-temporal spindle-ripple rates in the speech-dominant-hemisphere (left in all patients) were correlated with verbal memory test results, whereas ripple rates in the non-speech-dominant hemisphere were correlated with non-verbal memory test performance, using Spearman correlation).ResultsIntracranial EEG and memory test results from 25 patients could be included. All ripple rates were significantly higher in seizure onset zone channels (p < 0.001). Patients with pre-surgical verbal memory impairment had significantly higher overall ripple rates in left mesial-temporal channels than patients with intact verbal memory (Mann-Whitney-U-Test: p = 0.039). Spearman correlations showed highly significant negative correlations of the pre-surgical verbal memory performance with left mesial-temporal spike associated ripples (rs = -0.458; p = 0.007) and overall ripples (rs = -0.475; p = 0.006). All three ripple types in right-sided mesial-temporal channels did not correlate with pre-surgical nonverbal memory. No correlation for the difference between post- and pre-surgical memory and pre-surgical spindle-ripple rates was seen in patients with left-sided temporal or mesial-temporal surgery.DiscussionThis study fails to establish a clear link between memory performance and spindle ripples. This highly suggests that spindle-ripples are only a small portion of physiological ripples contributing to memory performance. More importantly, this study indicates that spindle-ripples do not necessarily compromise the predictive value of ripples in patients with temporal epilepsy. The majority of ripples were clearly linked to areas with poor memory function.

Dataset Information

Left hemispheric ? band cerebral oscillatory changes correlate with verbal memory.

Publications

Left hemispheric α band cerebral oscillatory changes correlate with verbal memory.

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