Convergent effects of different anesthetics on changes in phase alignment of cortical oscillations

"They indicate decreased phase alignment between ventrolateral and dorsolateral arrays (L-Ven vs. L-Dor, R-Ven vs. R-Dor; Figure 1C, green). By contrast, there was increased phase alignment across hemispheres (L-Ven vs. R-Ven, L-Dor vs. R-Dor; Figure 1C, purple)... Anesthetic doses of both ketamine and dexmedetomidine caused a significant decrease in phase alignment within hemispheres... Across hemispheres, there was a significant increase in phase alignment..."

Anesthetics reduced alignment within hemispheres but increased it across hemispheres, p. 3

Direct evidence that anesthesia reconfigures the timing relationships of slow oscillations—desynchronizing within-hemisphere and synchronizing across hemispheres—supports a key role for temporal coordination mechanisms in transitions of conscious state.

"PLV, coherence, and phase offset were calculated between pairs of channels on indicated arrays... To calculate the PLV, we took the absolute value of the average normalized cross spectrum. To calculate coherence, we divided the cross spectrum of two channels by the square root of the product of each channel’s auto spectrum. To calculate the phase offset, we took the angle of the cross spectrum."

PLV, coherence, phase offset, p. 11

The methodological details confirm that time-resolved phase coordination was quantified with standard PLV/coherence metrics appropriate for assessing oscillatory synchronization relevant to conscious processing.

Figures

Figure 2 (p. 4) : Shows anesthesia-amplified distance-dependent desynchronization within arrays, linking spatial scale to the timing structure of oscillations implicated in conscious state changes.

"Within a hemisphere, the ventrolateral and dorsolateral PFC became less phase aligned at low frequencies... These offsets may fragment within-hemisphere communication as periods of excitability become misaligned... In contrast to the fragmentation of activity within a hemisphere, homologous regions across hemispheres became more aligned."

Discussion, p. 5

Authors interpret the altered phase relationships as degrading local integrative communication while enhancing synchrony across hemispheres, mapping oscillatory coordination changes onto information-integration/segregation relevant to consciousness.

"Such synchrony could also be partially mediated by subcortical regions like the thalamus, a potential hub of interhemispheric communication... low-frequency oscillations and thalamocortical connections may be involved in information transfer between cortical regions, which may be disrupted during anesthesia, thus leading to unconsciousness."

Discussion, p. 5

Links the observed network-level phase patterns to thalamocortical routing of information, suggesting a mechanism by which integration is compromised during anesthesia-induced unconsciousness.

Figures

Figure 3 (p. 6) : Dose-dependent weakening of the phase changes supports a graded disruption of integrative dynamics, consistent with reduced alteration of information flow at sub-anesthetic levels.