Biology subjects

Seifpour, S.

Publications and source records attributed to Seifpour, S..

3 recordsLinked to original sources

bioRxiv2026

Stimulus predictability rather than inter-trial interval itself affects motor evoked potential amplitudes

The inter-trial interval (ITI) of transcranial magnetic stimulation (TMS) can modulate motor-evoked potential (MEP) amplitude and may thus confound assessments of corticospinal excitability. We tested whether this effect depends on the ITI duration per se or the associated temporal predictability and whether intracortical inhibitory processes mediate these effects on. In 26 healthy participants, we recorded single-pulse MEPs and paired-pulse measures of short-interval intracortical inhibition (SICI; 2-ms interstimulus interval) and long-interval intracortical inhibition (LICI; 100-ms interstimulus interval) at ITIs of 2, 5, and 10 s. ITIs were presented in different Patterns, i.e., separate fixed blocks (FXD), randomly intermingled within blocks (RND), or randomly intermingled but auditorily cued at 950 ms pre-TMS (RNDC). MEPs showed significant effects of ITI, Pattern, and their interaction, being smaller at 2 s than at longer ITIs in FXD but not in RND and RNDC. However, RNDC produced marked MEP suppression across all ITI. SICI showed a Pattern x ITI interaction but no main effect of Pattern or between-pattern differences per ITI, whereas LICI showed complex Pattern x ITI interaction and both main effects. Notably, ITI affected SICI and LICI oppositely. While GABA-A-receptor mediated inhibition (SICI) showed an ITI dependency compatible with the ITI effects on single-pulse MEPs, it was unlikely mediating the predictability effects but may rather relate to an independent ITI driven suppression. In contrast, GABA-B-receptor mediated inhibition (LICI), was clearly modulated by predictability, but incompatible with the observed ITI effects on MEP amplitude. In summary, the effect of ITI duration on MEP amplitude seems to be largely explained by anticipatory suppression of corticospinal excitability based on the predictability of TMS pulses as derived from their temporal context, being easier for shorter and more regular ITIs and maximal for explicit cues immediately preceding the TMS pulse. SICI and LICI are modulated by ITI as well, with the latter affected by predictability, but neither can explain the observed predictability effects on single-pulse MEP amplitudes.

neuroscience↗

bioRxiv2026

Suppression of corticospinal excitability by sleep spindles without increase in GABAergic inhibition

Thalamocortical sleep spindles are hypothesised to support memory consolidation during sleep by creating transient windows of enhanced hippocampal-neocortical communication and synaptic plasticity. A recent real-time electroencephalography (EEG)-triggered transcranial magnetic stimulation (TMS) study found a pulsed suppression of corticospinal excitability during spindles relative to spindle-free non-rapid eye movement (NREM) sleep, driven by the spindle falling phase. We hypothesised that this phasic suppression may reflect local inhibitory network dynamics, measurable as GABA-A receptor-mediated short-interval intracortical inhibition (SICI) using paired-pulse TMS. We applied real-time EEG-triggered single- and paired-pulse TMS over the primary motor cortex during pre-sleep wakefulness, spindle-free N2/N3 sleep, and at four sleep spindle phases (peak, falling, trough, and rising). Corticospinal excitability was strongly reduced from wakefulness to spindle-free N2/N3 sleep, and further suppressed during sleep spindles. Numerically, excitability was lowest during the falling phase and trough, although we found no significant modulation across spindle phases. Contrary to our hypothesis, neither spindle presence nor phase significantly modulated SICI. Secondary analyses provided preliminary evidence that slow oscillations present at stimulation increased excitability and reduced SICI, irrespective of spindle presence. Together, these findings indicate distinct contributions of sleep/wake vigilance states, sleep spindles, and slow oscillations to cortical network dynamics, and provide new insight into the transient modulation of corticospinal excitability and GABA-A-receptor mediated SICI during human NREM sleep.

neuroscience↗

bioRxiv2026

Boredom and the representation of information content in the neocortex

Boredom - a pervasive mental state - promotes the pursuit of novel information by assigning negative value to monotonous conditions. Yet, how the brain extracts and represents the information content of ongoing sensory experience remains poorly understood. Here, we combine behavioral assays, neurophysiological recordings and computational modeling across humans and mice to investigate how sensory information shapes boredom-related behavior. In a cross-species choice task, both humans and mice robustly avoid monotonous sources of sensory stimulation. We formalize perceived monotony using empirical entropy as a measure of information content and show that monotony avoidance scales directly with low entropy and in humans correlates with boredom experience. Human electroencephalography and mesoscopic calcium imaging in mice reveal that the recruitment of neocortical activity tracks stimulus entropy. Two-photon calcium imaging in the auditory cortex of mice further uncovers a stimulus-invariant population code for entropy, supported by neurons tuned to information content. A recurrent network model reproduced this code through an interplay of afferent depression and recurrent facilitation. Together, we demonstrate how the information content of sensory experience is represented in cortical population activity, providing a basis for boredom-related avoidance behavior. Thus, our findings link synaptic and neuronal dynamics to boredom, acting as a safeguard mechanism to ensure high information input to the brain.

neuroscience↗