Topic: population code

To orchestrate complex behaviors in mammals, the cerebral cortex must continuously transmit its processing results to subcortical regions. While internal cortical processing relies on highly selective sparse codes, these descending cortical output streams employ an enigmatic dense code, characterized by high firing rates and low feature selectivity. This dense population code presents a profound paradox: how can downstream regions extract precise, cognitively relevant signals when most cortical output neurons can be active at any moment? We address this paradox by testing the hypothesis tha

Neuronal computations are matched to optimally encode the sensory information that is available and relevant for the animal. However, the physical distribution of sensory information is often shaped by the animal’s own behavior. One prominent example is the encoding of optic flow fields that are generated during self-motion of the animal and will therefore depend on the type of locomotion. How evolution has matched computational resources to the behavioral constraints of an animal is not known. Here we use in vivo two photon imaging to record from a population of >3.500 local-direction selecti

Entorhinal grid cells, so-called because of their hexagonally tiled spatial receptive fields, are organized in modules which, collectively, are believed to form a population code for the animal’s position. Here, we apply topological data analysis to simultaneous recordings of hundreds of grid cells and show that joint activity of grid cells within a module lies on a toroidal manifold. Each position of the animal in its physical environment corresponds to a single location on the torus, and each grid cell is preferentially active within a single “field” on the torus. Toroidal firing positions p

Having conscious experience is arguably the most important reason why it matters to us whether we are alive or dead. A powerful paradigm to identify neural correlates of consciousness is binocular rivalry, wherein a constant visual stimulus evokes a varying conscious percept. It has recently been suggested that activity modulations observed during rivalry may represent the act of report rather than the conscious percept itself. Here, we performed single-unit recordings from face patches in macaque inferotemporal (IT) cortex using a novel no-report paradigm in which the animal’s conscious perce

The involvement of early visual cortex during the short-term maintenance of visual information has been demonstrated in human fMRI studies [1,2]. However, evidence for sustained, stimulus-related neuronal firing in primate V1 is limited [3,4]. Recently, fading traces of visual information have been shown in the population code of primate V1 neurons for ~1.5 seconds after visual stimulus presentation in delayed match to sample and attention tasks [5]. The relatively long time-course of these fading memories make it unlikely to be a neural correlate of iconic memory [6], but may be related to “f

A hallmark of biological and artificial neural networks is that neurons tile the range of continuous sensory inputs and intrinsic variables with overlapping responses. It is characteristic for the underlying recurrent connectivity in the cortex that neurons with similar tuning predominantly excite each other. The reason for such an architecture is not clear. Using an analytically tractable model, we show that it can naturally arise from a cooperative coding scheme. In this scheme neurons with similar responses specifically support each other by sharing their computations to obtain the desired

Our ability to recognize objects and natural scenes whether depicted in photographs, cartoons, or just line drawings (a.k.a. visual cues) is remarkable. Here, we investigated the representation of a set of surface boundary shapes rendered in different visual cues by macaque V1 and V2 neurons. Specifically, we investigated whether the geometric structure of the population code could support the formation of a cue-invariant representation of abstract surface boundary concepts. A visual concept refers to an abstract feature, such as a boundary or contour, that remains consistent across different