Whisker movements evoked by stimulation of single pyramidal cells in rat motor cortex

Abstract

Neuronal activity in the motor cortex is understood to be correlated with movements, but the impact of action potentials (APs) in single cortical neurons on the generation of movement has not been fully determined. Here we show that trains of APs in single pyramidal cells of rat motor cortex can evoke long sequences of small whisker movements. For layer-5 pyramids, we find that evoked rhythmic movements have a constant phase relative to the AP train, indicating that single layer-5 pyramids can reset the rhythm of whisker movements. Action potentials evoked in layer-6 pyramids can generate bursts of rhythmic whisking, with a variable phase of movements relative to the AP train. An increasing number of APs decreases the latency to onset of movement, whereas AP frequency determines movement direction and amplitude. We find that the efficacy of cortical APs in evoking whisker movements is not dependent on background cortical activity and is greatly enhanced in waking rats. We conclude that in vibrissae motor cortex sparse AP activity can evoke movements.

Characterization of some morphological parameters of orbicularis oculi motor neurons in the monkey

“…However, it has also been shown that to a lesser extent, OO activation can occur following direct stimulation of M1 (Woolsey et al, 1979;Benecke et al, 1988;Cruccu et al, 1990;Roedel et al, 2001;Sohn et al, 2004;Paradiso et al, 2005) and deficits transpire in OO function following damage to M1 that are less notable than perioral deficits, but are nonetheless detectable (Kojima et al, 1997). Collectively this observation may contribute to the complex nature of facial expression and possibly add to the inherent difficulties in isolating distinct, individuated facial muscle contractions following cortical stimulation (Woolsey et al, 1952;Strick and Preston, 1979;McGuinness et al, 1980;Brecht et al, 2004;Schieber, 2004).…”

Cortical neural populations can guide behavior by integrating inputs linearly, independent of synchrony

“…In addition to this nonlinearity caused by spike threshold, other active processes such as dendritic calcium spikes (3)(4)(5) can preferentially amplify synchronous inputs. A variety of ways that timing could impact network function have been explored, including oscillatory synchronization (6,7), strong cascading effects of individual neurons or synapses (8)(9)(10)(11), and information encoding via temporal patterns (12). In the songbird, for example, song neurons receive precisely timed coincident input that recruits active calcium conductances, generating strong, reliable spike bursts that control the song (13,14).…”

Representation of Sounds in Auditory Cortex of Awake Rats (Dissertation)

“…Experimental evidence for sparse coding has been found in a range of experimental preparations, including the visual (Baddeley et al, 1997;Vinje and Gallant, 2000), motor (Brecht et al, 2004), barrel (Margrie et al, 2002) and olfactory systems (Perez-Orive et al, 2002;Rinberg et al, 2006;Szyszka et al, 2005), the zebra finch auditory system (Hahnloser et al, 2002), and cat LGN (Dan et al, 1996).…”

“…At the other extreme, the neural representation could be sparse, at any moment in time engaging only a small fraction of neurons, each highly selective with a narrow receptive field. Although a dense code under some conditions makes the most efficient use of the "representational bandwidth" (DeWeese et al, 2005) available in a neuronal population-why should a large fraction of neurons remain silent most of the time?-sparse models have recently gained support on both theoretical (Asari et al, 2006;Olshausen and Field, 2004;Smith and Lewicki, 2006) and experimental (Baddeley et al, 1997;Brecht et al, 2004;Dan et al, 1996;Hahnloser et al, 2002;Margrie et al, 2002;Szyszka et al, 2005;Vinje and Gallant, 2000) grounds. However, it is not at present clear which of these is a better model of sensory representations in the auditory cortex.…”

“…Whole-cell recordings in-vivo are very challenging, and their application in awake animals is technically difficult. Only very recently, several studies have described successful whole-cell recordings 8 in somatosensory (barrel) cortex of awake (unanesthetized) mice and rats (Brecht et al, 2004;Crochet and Petersen, 2006;Lee et al, 2006;Margrie et al, 2002;Petersen et al, 2003a). …”