Single Unit Electrophysiological Responses

Much of our understanding of neural function stems from electrophysiological studies of single neurons. By placing microelectrodes made of wire or drawn glass capillary tubing into or next to neurons, it is possible to record signals generated by one or a few cells. Because of the stereotypical shape and amplitude of action potentials (spikes) recorded from a given cell in a given recording configuration, it is often possible to sort a complex record into contributions from a small set of cells. The intensity of neuronal activation is typically assessed on the basis of firing rate; in sensory systems, the intensity of a stimulus is often encoded logarithmically in the firing rate within the sensory nerve. The response properties of neurons are often defined in terms of the receptive field, the region of sensory parameter space (e.g., location on the retina or stimulus properties of an auditory or visual stimulus) that can influence the firing rate of a particular neuron. A growing body of evidence shows that the temporal pattern of firing may also encode information. For example, in measurements across an ensemble of auditory nerve fibers in response to a pure tone stimulus below 1 kHz or so, spikes tend to occur in phase with the stimulus, i.e., a temporal code captures the temporal structure of the stimulus. In the visual system, phase-locked oscillatory activity in widely spaced cells appears to encode higher order features, such as coherent motion, beyond the spatial limits of the conventional receptive field.

Breaking Bulimia

Breaking Bulimia

We have all been there: turning to the refrigerator if feeling lonely or bored or indulging in seconds or thirds if strained. But if you suffer from bulimia, the from time to time urge to overeat is more like an obsession.

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