#Constricted pupil size free

Less is known about pupil responses during memory processing. Hence, pupillometry has become an attractive tool for accessing information about the brain states and neurophysiological processes supporting sensory perception, attention and decision-making. Furthermore, pupil size and these cortical arousal states were associated with slow and fast electrophysiological activities 9, 10 – low arousal and constricted pupil with low-frequency oscillations, compared with enhanced sensory responses, arousal and dilated pupil with high frequency oscillations. Tracking pupil dilation was shown to correlate with transitions in the cortical state as measured in the intracellular membrane potential across multiple brain regions 9. The tight link with these wide spread neuromodulatory systems inspired research into the relationship between the brain states, electrophysiological activities and the pupil response. Adrenergic and cholinergic neuromodulation has been implicated in the regulation of these pathways 5, 7 and, more generally, of the thalamo-cortical brain networks during states of sleep, wakefulness and cognition 8. The anatomy and physiology of the brain pathways controlling pupil size have been well described 6, and are known to involve both the autonomic and somatic nervous systems.

In these experiments, pupil size alone was able to predict an overt decision about timing an action and a covert decision about choice of the stimulus 5, suggesting a link between pupil responses and the higher-order brain systems supporting cognition, decision-making and/or execution of actions. More recent studies have shown that high-resolution tracking of pupil size can be used to predict perception of specific stimuli 4 and even the voluntary decisions about attending the stimuli 5. It is also known to indicate general mental activity and correlate with task difficulty 2, 3. Pupil dilation was shown to indicate interest in the content of the presented visual stimuli, which revealed sex-specific differences 1. Pupil size has been associated with cognitive processes underlying perception, attention and action for external stimuli. Our results suggest pupil size as a potential biomarker for probing and modulation of memory processing.

Words that were successfully recalled showed significant differences in pupil response during their encoding compared to those that were forgotten – the pupil was more constricted before and more dilated after the onset of word presentation. Within the final recall phase, retrieving memory for individual words was associated with pupil dilation in absence of visual stimulation. The pupil was most constricted in the initial fixation phase and was gradually more dilated through the subsequent encoding, distractor and recall phases of the task, as the word items were maintained in memory.

#Constricted pupil size free

Consistent patterns in the pupil response were found across and within distinct phases of the free recall task. Here we investigated changes in the pupil size during encoding and recall of word lists. They can provide an accessible biomarker of human memory performance and cognitive states in general. Pupil responses are known to indicate brain processes involved in perception, attention and decision-making.