Do you remember when…? Human beings rely on processing of temporal information on a variety of scales (from microseconds to years) and from a variety of sensory modalities, including timing of visual, auditory and somatosensory (touch-based) stimuli. Despite the significance of temporal information perception and processing to our existence, there is little consensus about the brain mechanisms responsible. Health © Shutterstock Many studies have focused on the sub-second time scale, for which subcortical mechanisms are most likely important. Others have focused on one input modality, for example visual or auditory input, which limits effective conclusions regarding general mechanisms. However, it has use in identifying cortical mechanisms associated with visual or auditory cortical regions, respectively. The ‘Neural bases of temporal processing in the human brain’ (Neurotime) project was designed to investigate neural mechanisms underlying temporal processing by combining different sensory modalities and different durations within the same set of experiments. The researchers hypothesised that generalised amodal (irrelevant of stimulus modality) and subcortical (e.g. cerebellar) mechanisms are involved in temporal processing of signals on the order of one to two seconds. Furthermore, they proposed that, for larger time scales, additional cortical areas such as visual cortex and auditory cortex as well as prefrontal and parietal cortices that register temporal information in memory are recruited. Following behavioural experiments involving both visual and auditory stimuli for both short (2 seconds) and long (12 seconds) durations, the investigators determined that individuals were highly consistent in time estimation across modalities, suggesting amodal mechanisms, but less consistent for short and long durations. They then collected structural magnetic resonance imagining (MRI) brain images of the participants to determine if the differences in processing of different durations were reliably associated with differences in neural structures. The Neurotime project addressed the important area of temporal signal processing in humans by evaluating two different durations of stimuli and using two sensory modalities (audio and visual). The experiments investigated both function, as evidenced by behavioural experiments, as well as structures related to functional processing via structural MRI in the same subjects. The results should advance our understanding of how – and where – human beings process important temporal information, whether it be sound localisation to avoid an oncoming car or storage of childhood memories.
