Past events

An extensive body of research has established that the hippocampus plays a pivotal role in the encoding of new associations. Yet it remains unclear how entire episodes that unfold over time are bound together in memory. Real-life episodes can be viewed as a sequence of interrelated episodic elements, and their encoding may be incremental, such that each element that is encountered is registered to memory. Conversely, the episode may be stored in a temporary buffer and registered to long-term memory as a cohesive unit when it has come to closure. Using short film clips as memoranda, we find that hippocampal encoding-related activity is time-locked to the offset of the event, potentially reflecting the encoding of a bound representation to long-term memory. Notably, when distinct clips were presented in immediate succession, the hippocampus responded at the offset of each event, suggesting hippocampal activity is triggered the occurrence of event boundaries (transition between events). However, while brief film clips mimic several aspects of real-life, they are still discrete events. To determine whether event boundaries drive hippocampal activity in an ongoing experience, we analysed brain activity of over 200 participants who viewed a naturalistic film and found that the hippocampus responded both reliably and specifically to shifts between scenes. Taken together, these results suggest that during encoding of a continuous experience, event boundaries drive hippocampal processing, potentially supporting the transformation of the continuous stream of information into distinct episodic representations.

It is established that the brain is capable of large-scale reorganization following sensory deprivation or injury. What is less clear is what are the rules that guide it. In the blind, many visual regions preserve their task specificity despite being recruited for different sensory input; ventral visual areas, for example, become engaged in auditory and tactile object-recognition. However, we are interested in two questions. First, is sensory deprivation necessary for such task-specific reorganization, or can it happen in non-deprived individuals? In this series of experiments, during 9 months we taught Braille, a tactile alphabet, to sighted individuals and observed the resulting changes with structural and functional MRI. (Siuda, Krzywicka, Bola et al, eLife, 2016). Second, we wondered whether task-specific reorganization is unique to the visual cortex, or alternatively, is it a general principle applying to other cortical areas. Here, we enrolled deaf and hearing adults into an fMRI experiment, during which they discriminated between rhythms. In hearing individuals, rhythm processing is performed mostly in the auditory domain. Our prediction was that if task-specific reorganization applies to the human auditory cortex, performing this function visually should recruit the auditory cortex in the deaf (Bola, Zimmerman et al., PNAS, 2017).

Mammalian whiskers and avian rictal bristles come in a variety of shapes and sizes. Indeed, one of the most striking facial features in all mammals (excluding higher primates and humans) is the presence of whiskers. They are deployed in a wide range of tasks and environments. For example, rodents may use their whiskers to guide arboreal locomotion, whilst seals use theirs to track hydrodynamic trails of vortices shed by the fish upon which they prey (Gläser et al, 2010). Certainly, the evolution of the sense of touch is a recognised cornerstone in mammalian evolution, driving brain complexity and behavioural flexibility. While the whisker system is an established model for sensory information processing, advances in measuring whisker behaviours suggests that whisker movements are also useful for measuring aspects of motor control. Many "whisker specialists" including rodents and pinnipeds employ their whiskers by moving them actively, and all mammals (and even some birds) share a similar muscle architecture that drives the movement of the whiskers. Certainly, changes in whisker movements can indicate a loss of motor control and coordination. In this talk I will consider the anatomy and morphology of whiskers, and consider their function in a range of different species. I will suggest how whisker movements may have evolved, and how they are very important for whisker specialists.