Wow! As always, SfN 2016 was a completely full-on experience. This year was in San Diego, which is obviously the only appropriate location for a conference of that size that is consistently held in October/November. Saturday afternoon featured a ‘Temporal Processing’ poster session, which looked excellent. The session included work from labs around the world presenting on a great range of timing-related topics. Unfortunately (but also fortunately), I presented my own poster during this session and so saw zero other posters. But it’s good to be busy during your own poster session. The highlight for me was that many from the session joined for a post-poster drink, so there was still an opportunity to interact with many presenters and their co-authors, some more scientifically and some more socially. There was also a session on ‘Neural Circuits for Timing, Temporal Processing, and Sequences’ on Tuesday afternoon and another ‘Temporal Processing’ session Wednesday morning. And I’m sure there were uncountable things I missed.
The most inspiring thing I personally saw at SfN was a talk by Flavio Fröhlich in a symposium on “Advances in Noninvasive Brain Stimulation Along the Space-Time Continuum”. Although neither the symposium nor the talk were on timing per se, I think the sky is the limit in terms of applying noninvasive brain stimulation techniques to understand the neural bases of timing, most obviously in the domain of rhythm and beat perception, where neural oscillations and neural entrainment might be manipulated. The talk (“From biophysics to treatment: rational design of non-invasive brain stimulation to modulate thalamo-cortical oscillations”) provided a rapid-fire introduction to work in the Fröhlich lab spanning levels from mathematical/computational modeling of thalamocortical circuits to clinical trials testing the efficacy of noninvasive brain stimulation for post-traumatic stress disorder and depression (and covering everything in between).
All of the work builds from the idea that ongoing neural oscillations can be “picked up”, or entrained, by noninvasive brain stimulation. The novel insight that it provided though, which is simultaneously completely obvious and not obvious at all (at least for me), is that it’s not necessarily sufficient to blast a brain with stimulation in order to cause entrainment or to cause the presence of a neural oscillation of a particular frequency. If the target neural signal isn’t present at the time stimulation is applied, we can’t expect it to be entrained or enhanced. For example, applying noninvasive brain stimulation that mimics the shape of sleep spindles to an awake person doesn’t do much. But, when applied to a sleeping person for whom sleep spindles are naturally present, transcranial alternating current stimulation (tACS) that enhances those sleep spindles actually enhances motor memory, in particular when the stimulation is specially designed to match the sleep spindles of that particular person! Despite being completely mind-blowing, this actually makes complete sense from a dynamical systems perspective.
Given the current hype surrounding the involvement of neural oscillations and neural entrainment in rhythm and beat perception (into which I definitely buy), it seems that a natural next step is in the direction of noninvasive brain stimulation techniques (and in particular what one might think of as “time-domain” techniques, such as tACS). Can we shift the metrical interpretation or phase alignment of the beat in an ambiguous rhythm?; can we disrupt the perception of a beat altogether?; can we improve beat perception for syncopated rhythms or for individuals that are weak beat perceivers to begin with? All of these would contribute to our understanding of how neural oscillations and entrainment are related to beat perception. But I think the key take-away message from the talk is that null results cannot and should not be interpreted as evidence that brain stimulation won’t deliver answers to these questions (a problem very much not specific to brain stimulation or beat perception). Instead, whether the neural “conditions” are right should be at the center of any forays we make into the world of noninvasive brain stimulation. I suggest that this might require paying careful attention to individual differences, which are very apparent in the context of rhythm and beat perception – this is in line with growing interest in personalized medicine. Tuning our approaches by knowing about the neural preferences an individual person in a particular context may allow us to develop more effective treatments to improve, for example, movement and gait in Parkinson’s disease or memory in Alzheimer’s disease.
– Molly Henry, University of Western Ontario