Journal of Neuroscience
February 8, 2017
Jason Samaha, Olivia Gosseries, Bradley R. Postle
131 citations
Transcranial magnetic stimulation (TMS) of occipital and posterior parietal cortex can produce visual sensations called phosphenes. Using near-threshold TMS with concurrent EEG, the authors found that prestimulus power and phase in the alpha band (8–13 Hz) predicted occipital TMS phosphenes, while higher-frequency beta-band (13–20 Hz) power (but not phase) predicted parietal TMS phosphenes. TMS-evoked responses related to phosphene perception were similar across sites, showing an early posterior negativity and later parietal positivity, plus low-frequency power increase followed by broadband alpha/beta power decrease. These correlates resemble those of conscious perception of near-threshold visual stimuli. The regionally differential prestimulus predictors suggest distinct frequencies reflect cortical excitability in occipital versus parietal cortex, challenging the assumption that alpha rhythm serves as a general index of cortical excitability.
Psychological review
March 1, 2024
Manoj K Doss, Jason Samaha, Frederick S Barrett et al.
24 citations
Psychoactive drugs produce unique subjective states, but their effects on episodic memory often overlap. This reanalysis of 10 data sets (28 drug conditions) used signal detection models to separate three memory processes: recollection (retrieving specific details), familiarity (recognizing without details), and metamemory (introspecting about memory accuracy). Sedatives impaired both recollection and familiarity during encoding but enhanced recollection during consolidation. Dissociatives and cannabinoids impaired recollection during encoding, and cannabinoids increased false recollections during retrieval. Psychedelics impaired recollection during encoding but tended to enhance familiarity. Stimulants enhanced metamemory during encoding and retrieval but impaired metamemory during consolidation. These distinct patterns help explain drug-specific phenomena like sedative-induced blackouts and psychedelic presque vu, and suggest that memory quantity and stability influence metamemory.
bioRxiv (Cold Spring Harbor Laboratory)
May 24, 2022
Manoj K. Doss, Jason Samaha, Frederick S. Barrett et al.
6 citations
preprint
Different classes of psychoactive drugs—sedatives, dissociatives, psychedelics, stimulants, and cannabinoids—each produce unique patterns of effects on the conscious processes underlying episodic memory, depending on whether they act during encoding, consolidation, or retrieval. Reanalyzing confidence data from 10 published datasets (28 drug conditions) with signal detection models, the authors found that all drugs except stimulants impaired recollection when given at encoding; sedatives, dissociatives, and cannabinoids also impaired familiarity at encoding. Psychedelics at encoding enhanced familiarity and did not affect metamemory, while dissociatives and cannabinoids tended to enhance metamemory. Stimulants enhanced metamemory at encoding and retrieval but impaired it at consolidation. These distinct profiles may help explain drug-specific subjective phenomena such as sedative-induced blackouts or psychedelic déjà vu.