Single Unit Responses

Crapper and Tomko examined the single unit response of visual neocortical neurons in aluminum-treated cats. Spike discharges were collected for 10-120 min and the mean spontaneous fre- 

They also observed a 10% reduction in the percentage of neurons with spontaneous mean frequencies less than 2.5. They interpret their finding, in light of other evidence, as suggesting that aluminum, at least in its early stages, reduces the spontaneous discharge rate. 

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Rebec, G.V., and Gardiner, T.W. Regional effects of amphetamine in the neostriatum Single unit responses in freely moving rats. Abstr Soc Neurosci 11 550, 1985. 

Fig. 5.5(b) Single unit responses in neocortex of dog effect of N-P duct closure [= columns] on response to conspecific odours. Ou = own urine, Of = own faeces, Su = strange urine, Sf = strange faeces, and C. = dry food for dog (from Onoda et al., 1981). 

Meredith, M. Olfactory coding single unit response to amino acids in goldfish olfactory bulb. Ph.D. Thesis, University of Pennsylvania, 1974. 

In principle, the step-response coefficients can be determined from the output response to a step change in the input. A typical response to a unit step change in input u is shown in Fig. 8-43. The step response coefficients are simply the values of the output variable at the samphng instants, after the initial value y(0) has been subtracted. Theoretically, they can be determined from a single-step response, but, in practice, a number of bump tests are required to compensate for unanticipated disturbances, process nonhnearities, and noisy measurements. 

Przbyslawski J, Roullet P, Sara SJ (1999) Attenuation of emotional and nonemotional memories after their reactivation role of p adrenergic receptors. J Neurosci 19 6623-6628 Quirk GJ, Russo GK, Barron JL, Lebron K (2000) The role of ventral medial prefrontal cortex in the recovery of extinguished fear. J Neurosci 20 6225-6231 Rasmussen K, Marilak DA, Jacobs BL (1986) Single unit activity of the locus coeruleus in the freely moving cat. 1. Dming naturalistic behaviors and in response to simple and complex stimuli. Brain Res 371 324-334... 

In a third study, single unit recordings from the moth Heliothis virescens placed in a wind tunnel corroborated the previously described results by showing how well single neurons follow the fine-scale temporal characteristics of a natural odor plume (Vickers et al., 2001). Also in this study it was clear that the occurrence of a stimulus over time heavily influences the temporal structure of the response to a given stimulus. Both stimulus intensity and dynamics of the odor plume had an effect on the time course of the PN spike pattern. Furthermore, no wave-like periodicity in PN spiking could be observed and PN spike frequency did only rarely match the frequency range of local field potential oscillations that has been reported from moths (M. sexta Heinbockel et al., 1998). 

Experiments using extracellular single unit recordings of nucleus accumbens neurons in combination with chronoamperometric measures of dopamine efflux lead to a similar conclusion. Potentiation of hippocampal-evoked response is induced in accumbens cells by HFS of the fimbria. This potentiation was blocked by SCH23390 or an NMDA antagonist (Floresco et al., 2001), and is associated with a transient increase in dopamine concentration in the accumbens. Thus, as in the dorsal striatum, a transient increase in dopamine concentration which is time-locked to the HFS-induced depolarization of nucleus accumbens neurons, is sufficient to facilitate subsequent hippocampal-evoked activity. The subsequent release of dopamine after induction of this facilitation does not appear to play a role (Floresco et al., 2001). 

Figure 4 Electrically evoked single-unit tactile responses recorded with microwire multielectrode arrays in rat hippocampus CA1, primary somatosensory cortex, and ventral posteromedial nucleus brain regions. (Upper) Raster plot of single-unit spikes before and after electrical current stimulation to whiskers. Each row is a separate trial. (Lower) Summed activity for all trials in 1-ms bins that demonstrate a response to electrical stimulation. The graphs show different latencies in firing for the three different regions. [Data reprinted from Ref. (1 3). Copyright (2007) National Academy of Sciences, U.S.]...

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