Supramodality of neural entrainment: Rhythmic visual stimulation causally enhances auditory working memory performance.

The frontoparietal network is involved in multiple tasks, such as visual mental rotation, working memory, or arithmetic. Whether those different cognitive processes are supported by the same supramodal network or distinct, but overlapping, functional systems is unresolved. We investigate whether frontoparietal activity can be selectively entrained by rhythmic sensory stimulations (visual rotation) and whether this entrainment can causally modulate task performance in another modality (auditory working memory). We show that rhythmic visual presentations of rotating shapes, known to activate the dorsal pathway, increase frontoparietal connectivity at stimulation frequency as measured with MEG/EEG. We then show that frontoparietal theta oscillations predict auditory working memory performance. Last, we demonstrate that theta rhythmic visual stimulation applied during auditory memory causally enhances performance, and both the rotating properties of the stimulus and its flickering frequency drive the effect. This study provides causal evidence of the supramodal role of the frontoparietal network in human cognition.

Mapping the human auditory cortex using spectrotemporal receptive fields generated with magnetoencephalography.

We present a novel method to map the functional organization of the human auditory cortex noninvasively using magnetoencephalography (MEG). More specifically, this method estimates via reverse correlation the spectrotemporal receptive fields (STRF) in response to a temporally dense pure tone stimulus, from which important spectrotemporal characteristics of neuronal processing can be extracted and mapped back onto the cortex surface. We show that several neuronal populations can be found examining the spectrotemporal characteristics of their STRFs, and demonstrate how these can be used to generate tonotopic gradient maps. In doing so, we show that the spatial resolution of MEG is sufficient to reliably extract important information about the spatial organization of the auditory cortex, while enabling the analysis of complex temporal dynamics of auditory processing such as best temporal modulation rate and response latency given its excellent temporal resolution. Furthermore, because spectrotemporally dense auditory stimuli can be used with MEG, the time required to acquire the necessary data to generate tonotopic maps is significantly less for MEG than for other neuroimaging tools that acquire BOLD-like signals.

Loss of surface antigens is a conserved feature of apoptotic lymphocytes from several mammalian species.

Human lymphocytes lose the expression of lineage antigens (LAgs) along apoptosis. Our aim was to extent our previous studies of LAg loss to rodent species, quantifying LAg expression on apoptotic murine lymphocytes using flow cytometry to measure alterations in cell permeability, phosphatidylserine exposure and caspase activation of CD3, CD5, CD4, CD8, CD19 and CD28 LAgs in highly purified lymphocyte populations. We found loss of expression by apoptotic cells of all LAgs studied in the three species analyzed except for CD3 antigen in mouse. We also found an early, rapid and dramatic reduction in the expression of CD28 by early apoptotic cells. We found several homologies across the three species in the kinetic of loss of several LAgs such as CD5, CD4 and CD28. These data suggest that the loss of expression of LAgs by apoptotic lymphocytes is a common and conserved feature of lymphocytes undergoing apoptosis in several mammalian species.