Place cell activity of hippocampal pyramidal cells has been described as the cognitive substrate of spatial memory. Replay is observed during hippocampal sharp-wave-ripple-associated population burst events (PBEs) and is critical for consolidation and recall-guided behaviors. PBE activity has historically been analyzed as a phenomenon subordinate to the place code. Here, we use hidden Markov models to study PBEs observed in rats during exploration of both linear mazes and open fields. We demonstrate that estimated models are consistent with a spatial map of the environment, and can even decode animals’ positions during behavior. Moreover, we demonstrate the model can be used to identify hippocampal replay without recourse to the place code, using only PBE model congruence. These results suggest that downstream regions may rely on PBEs to provide a substrate for memory. Additionally, by forming models independent of animal behavior, we lay the groundwork for studies of non-spatial memory.
Attention selectively routes the most behaviorally relevant information from the stream of sensory inputs through the hierarchy of cortical areas. previous studies have shown that visual attention depends on the phase of oscillatory brain activities. these studies mainly focused on the stimulus presentation period, rather than the pre-stimulus period. Here, we hypothesize that selective attention controls the phase of oscillatory neural activities to efficiently process relevant information. We document an attentional modulation of pre-stimulus inter-trial phase coherence (a measure of deviation between instantaneous phases of trials) of low frequency local field potentials (LFP) in visual area Mt of macaque monkeys. our data reveal that phase coherence increases following a spatial cue deploying attention towards the receptive field of the recorded neural population. We further show that the attentional enhancement of phase coherence is positively correlated with the modulation of the stimulus-induced firing rate, and importantly, a higher phase coherence is associated with a faster behavioral response. these results suggest a functional utilization of intrinsic neural oscillatory activities for an enhanced processing of upcoming stimuli.One of the most important cognitive functions of the mammalian brain is selective attention. Attention selectively routes the most behaviorally relevant information from the stream of sensory inputs through the hierarchy of cortical areas. This allows the brain to make the most efficient use of its limited neural resources and to create appropriate behavioral responses quickly 1 . Attentional influences on neural responses in sensory cortex have been extensively documented; effects which reflect a multitude of aspects of cortical information processing 1-4 . Covertly directing attention towards the receptive field of a neuron in visual cortex enhances the neural responses even in the absence of visual stimulation 5,6 , alters the shape and profile of receptive fields 7-9 , modulates the variability and temporal structure of the neuron's firing patterns 10,11 , modulates inter-neuronal correlations to increase neural discriminability 12,13 and synchronizes neighboring neurons, presumably to better propagate information to downstream areas [14][15][16] .Attention has been suggested to exploit oscillatory neural activities, as well as oscillatory components of local field potentials (LFP), to enhance the efficacy of cortical processing 17-23 . LFPs represent synaptic activities of local cortical neuronal populations 24 . Their oscillations are tightly linked to attention in both low and high frequencies 18,[25][26][27][28][29] . Previous studies have shown that synchronization in the gamma as well as high gamma band
24Attention selectively routes the most behaviorally relevant information among the vast 25 pool of sensory inputs through cortical regions. Previous studies have shown that visual 26 attention samples the surrounding stimuli periodically. However, the neural mechanism 27 underlying this sampling in the sensory cortex, and whether the brain actively uses these 28 rhythms, has remained elusive. Here, we hypothesize that selective attention controls the 29 phase of oscillatory synaptic activities to efficiently process the relevant information in 30 the brain. We document an attentional modulation of pre-stimulus inter-trial phase 31 coherence (a measure of deviation between instantaneous phases of trials) at low 32 frequencies in macaque visual area MT. Our data reveal that phase coherence increases 33 when attention is deployed towards the receptive field of the recorded neural population. 34 We further show that the attentional enhancement of phase coherence is positively 35 correlated with the attentional modulation of stimulus induced firing rate, and 36 importantly, a higher phase coherence leads to a faster behavioral response. Our results 37 suggest a functional utilization of intrinsic neural oscillatory activities for better 38 processing upcoming environmental stimuli, generating the optimal behavior. 39 attention | local field potentials | phase coherence | reaction time | visual cortex 40 41 72 (Yamagishi et al., 2003). Although there is prominent evidence on attentional modulation of 73 low frequency amplitude, the role of low frequency phase in attentional processing is yet 74 controversial. 75 The phase of low frequency oscillations modulates local neural activities represented by 76 gamma band activity, which presumably enables distant brain regions to interact (Demiralp et 77 al. , 2007). Some studies have shown that the phase of ongoing neural oscillations is responsible 78 for periodic sampling by visual attention (Busch and VanRullen, 2010; VanRullen et al., 2011). 79Furthermore, the phase of low frequency oscillations facilitates information transfer and neural 80 coding in the brain (Voloh and Womelsdorf, 2016). Therefore, low frequency phase can enable 81 the neural system to prepare for processing upcoming sensory stimuli. 82Pre-stimulus neural activity has been shown to be a determinant of retrieving episodic memory, 83 perception of environmental information and attention-related variability in response speed 84 (Addante et al., 2011; Hanslmayr et al., 2013 Hanslmayr et al., , 2007 Shibata et al., 2008). Interestingly, it has 85 been shown that pre-stimulus brain activity causally determines visual perception (Dugué et 86 al., 2011). In addition, it has been shown that the phase of low frequency oscillations is 87 responsible for this causal relationship (Hanslmayr et al., 2013). Furthermore, attention has 88 been reported to determine the phase of low frequency neural oscillations in order to influence 89 neuronal responses and behavioral responses to external events (Lakatos et al.,...
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