Effect of Subthreshold Up and Down States on the Whisker-Evoked Response in Somatosensory Cortex

Abstract

Changes in spontaneous activity within the cortex recognized by subthreshold fluctuations of the membrane potential of cortical neurons modified the response of cortical neurons to sensory stimuli. Sensory stimuli occurring in the hyperpolarized "down" state evoked a larger depolarization and were more effective in evoking action potentials than stimuli occurring in the depolarized "up" state. Direct electrical stimulation of the thalamus showed the same dependence on the cell's state at the time of the stimulus, ruling out a strictly thalamic mechanism. Stimuli were more effective at triggering action potentials in the down state even during moderate de- or hyperpolarization of the somatic membrane potential. The postsynaptic potential (PSP) evoked from the down state was larger than the up state PSP but achieved about the same peak membrane potential, which was also near the reversal potential of the PSP (about -51 mV). Chloride loading shifted the reversal potentials of both the up state and the whisker-evoked PSP toward a more depolarized membrane potential. In addition, the threshold for action potentials evoked from the down state was lower than for spikes evoked in the up state. Thus the larger PSP from the down state may be caused by its larger driving force, and the state dependence of action potential generation in response to whisker stimulation may in part be related to a shift in threshold. Different mechanisms are therefore responsible for the state-dependence of PSP amplitude and the spike frequency response to the whisker stimulus.

Spinal Cord Injury Immediately Changes the State of the Brain

“…However, our results show that the increased cortical responses are directly related to the slower/more silent cortical spontaneous activity, thus offering an additional mechanism to explain immediate changes in cortical responses after deafferentation. In the rat somatosensory system, brief peripheral stimuli evoke larger cortical responses when the cortex is in a silent compared to an active state (Petersen et al, 2003;Sachdev et al, 2004), particularly when the stimuli themselves are able to trigger active states associated with the responses (Hasenstaub et al, 2007;Reig and Sanchez-Vives, 2007). This inverse relation between the level of spontaneous activity and the amplitude of evoked responses is clearly present in our data.…”

Entrainment of Slow Oscillations of Auditory Thalamic Neurons by Repetitive Sound Stimuli

“…Slow oscillations of neuronal membrane potential between the up and down states at frequencies Ͻ1 Hz have been observed in various regions of the brain during slow wave sleep (Steriade et al, 1993a;Timofeev et al, 2001) or under anesthesia (Steriade et al, 1993b,c;Wilson and Kawaguchi, 1996;Anderson et al, 2000;Petersen et al, 2003;Sachdev et al, 2004). Even in awake animals, similar membrane potential fluctuations have been observed (Timofeev et al, 2001;Kitano et al, 2002;Petersen et al, 2003), but the durations of the up and down states tend to be shorter, typically on the order of tens of milliseconds (Steriade et al, 1993a;Timofeev et al, 2001;Destexhe and Sejnowski, 2003).…”

“…Slow oscillations in many brain regions interact strongly with sensory-evoked responses (Arieli et al, 1996;Petersen et al, 2003;Sachdev et al, 2004). For example, recordings from anesthetized or awake rats showed that whisker stimulation evoked larger depolarizing postsynaptic potentials and more spikes in cortical cells in the down state than in the up state (Petersen et al, 2003;Sachdev et al, 2004).…”

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

“…Up and down states have been described and characterized for several decades (Cowan and Wilson, 1994;Steriade et al, 1993a,b;Wilson and Groves, 1981). More recently, the bistability of the membrane potential has been described in-vitro (Cossart et al, 2003;Sanchez-Vives and McCormick, 2000), as well as in-vivo in frontal cortical areas (Lewis and O'Donnell, 2000;Léger et al, 2005), somatosensory (Petersen et al, 2003a;Sachdev et al, 2004;Steriade et al, 2001;Timofeev et al, 2001), visual (Anderson et al, 2000;Lampl et al, 1999), olfactory (Luo and Katz, 2001;Margrie and Schaefer, 2003), other areas (Paré et al, 1998), and striatum (Kasanetz et al, 2002;Mahon et al, 2003;Stern et al, 1997;Wilson and Kawaguchi, 1996).…”

“…Large, persistent changes in membrane potential can also occur in a response to behavioral state changes , or sensory stimulation (Anderson et al, 2000;Carandini and Ferster, 1997). Up and down states have been observed in frontal cortical areas (Lewis and O'Donnell, 2000;Léger et al, 2005), somatosensory (Sachdev et al, 2004;Steriade et al, 2001), visual (Lampl et al, 1999), olfactory areas (Luo and Katz, 2001;Margrie and Schaefer, 2003), striatum (Stern et al, 1997;Wilson and Kawaguchi, 1996), and many others.…”