How does the brain process time?

Chairs:  Jennifer Coull & Laurence Casini
Aix-Marseille Université & CNRS, Marseille, France


Abstract:

Timing the duration of perceptual or motor events is integral to a wide variety of cognitive processes, from language comprehension to action planning to decision-making. These processes all depend upon an implicit, or automatic, use of temporal information for their successful execution. Yet we also have access to a more conscious perception of the passage of time itself. But despite this "sense" of time, there are no sensory receptors specifically dedicated for perceiving time. Moreover, there are no neurological or psychiatric disorders characterised by timing dysfunction in the way that, for example, spatial impairments characterise unilateral neglect. So how is time represented in the brain? We address this issue by bringing together experts in the field who study time from a variety of different theoretical and methodological viewpoints. Data from patients with Parkinson's Disease or focal brain lesions will be considered along with functional imaging and electrophysiological data to try and identify the neural substrates of timing.

Talk 1:

The basal ganglia and temporal processing: evidence from Parkinson's disease

Marjan Jahanshahi
UCL Institute of Neurology, UK

Parkinson’s disease (PD) is characterized by basal ganglia dysfunction due to dopamine loss, which makes it an ideal ‘model’ for investigating the role of the basal ganglia and dopamine in temporal processing. Furthermore, bradykinesia, or slowness of movement, is one of the primary symptoms of PD and leads to the prediction of timing deficits in this disorder. Empirical evidence has established that patients with Parkinson’s disease have deficits in both motor timing and perceptual timing tasks, which increase with severity of the motor symptoms. Temporal processing in both the millisecond and seconds ranges is impaired in this disorder. These deficits in temporal processing are generally more severe off levodopa medication and are reduced when patients are tested on medication. Imaging of PD patients during performance of a synchronization-continuation motor timing task has shown that while the fronto-striatal circuits are engaged during performance of this task by healthy controls, PD patients rely on activation of the cerebellum for task performance. Dopamine replacement medication increases striatal and frontal activation and striatal-frontal connectivity in PD during motor timing compared to when tested off medication.
While evidence from PD has confirmed the importance of the basal ganglia and dopamine in temporal processing, the specific and differential roles that the striatum and the frontal areas play in temporal processing remain to be clarified.

Talk 2:

Does the processing of segmental durations in speech engage a general timer ?

Laurence Casini
LNC, Aix-Marseille Université & CNRS, Marseille, France

The duration of speech segments plays a critical role in the perceptual identification of these segments, and therefore in that of spoken words. Although it is obvious that timing is necessary for its perception and production, this temporal dimension has often been ignored in the study of language. Therefore, an important question is whether these mechanisms are specific to speech, or whether the perceptual handling of segment duration is accomplished by means of central timing mechanisms. Here, we will present and discuss some data centered on this question. In the first study, we investigated whether attentional manipulations known to affect explicit temporal processing similarly affect the perception of duration of speech, and in the second one, we studied effects of hyperstimulation of striatal dopamine receptors induced by sleep deprivation.
Results suggest that duration perception in language share common mechanisms with explicit temporal processing. In addition, the durations involved in speech perception being sub-second durations, these results also provide arguments to propose that sub- and supra-seconds durations could share common mechanisms.

Talk 3:

Automatic and controlled mechanisms in temporal perception

Angel Correa
Departemento de Psicologia experimental, Universidad de Granada, Granada, Spain

In this talk I will present evidence from electroencephalography and neuropsychology dissociating automatic and controlled temporal preparation. Controlled temporal preparation (temporal orienting of attention) requires a functional right prefrontal cortex and competes for central resources when performed concurrently with a working memory task. Automatic temporal preparation (regular rhythms and foreperiod sequential effects) does not involve the right prefrontal cortex, it survives from dual task interference, and it suppresses rather than enhances brain electrophysiological activity related to early auditory processing.

Talk 4:

Spatial-temporal interactions in the human brain: neurophysiological and neuropsychological studies.

Massimiliano Oliveri
Psychology Department, Università di Palermo, Palermo, Italy

Increasing evidence indicates that the representations of space and time interact in the brain but the exact neural correlates of such interaction remain unknown. . Psychophysical experiments document the presence of spatially localised distortions of sub-second time intervals and suggest that visual events are timed by neural mechanisms that are spatially selective. Experiments with supra-second intervals suggest that time could be represented on a mental time-line ordered from left-to-right, similar to what is reported for other ordered quantities, such as numbers. Neuroimaging and neuropsychological studies show that processing of temporal information recruits a distributed network in the right hemisphere and suggest a link between deficits in spatial attention and deficits in time perception. However, studies on patients with focal brain lesions suggest that while a right hemispheric network is critical for explicit timing, a left hemispheric network is necessary for mediating the effects of prismatic adaptation on spatial and temporal perception, as well as for implicit timing.