Evoked Oscillations in the Thalamo-Cortical Auditory System Are Present in Anesthetized but not in Unanesthetized Rats

Abstract

This study investigated the relative importance of central and peripheral signals for movement-related gating by comparing the time course and magnitude of movement-related decreases in tactile detection during a reference motor task, active isotonic digit 2 (D2) abduction, with that seen during three test tasks: a comparison with active isometric D2 abduction (movement vs. no movement) evaluated the contribution of peripheral reafference generated by the movement to gating; a comparison with passive D2 abduction (motor command vs. no motor command; movement generated by an external agent) allowed us to evaluate the contribution of the central motor command to tactile gating; and finally, the inclusion of an active "no apparatus," or freehand, D2 abduction task allowed us to evaluate the potential contribution of incidental peripheral reafference generated by the position detecting apparatus to the results (apparatus vs. no apparatus). Weak electrical stimuli (2-ms pulse; intensity, 90% detected at rest) were applied to D2 at different delays before and after movement onset or electromyographic (EMG) activity onset. Significant time-dependent movement-related decreases in detection were obtained with all tasks. When the results obtained during the active isotonic movement task were compared with those obtained in the three test tasks, no significant differences in the functions describing detection performance over time were seen. The results obtained with the isometric D2 abduction task show that actual movement of a body part is not necessary to diminish detection of tactile stimuli in a manner similar to the decrease produced by isotonic, active movement. In the passive test task, the peak decrease in detection clearly preceded the onset of passive movement (by 38 ms) despite the lack of a motor command and, presumably, no movement-related peripheral reafference. A slightly but not significantly earlier decrease was obtained with active movement (49 ms before movement onset). Expectation of movement likely did not contribute to the results because stimulus detection during sham passive movement trials (subjects expected but did not receive a passive movement) was not different from performance at rest (no movement). The results obtained with passive movement are best explained by invoking backward masking of the test stimuli by movement-related reafference and demonstrate that movement-related reafference is sufficient to produce decreases in detection with a time course and amplitude not significantly different from that produced by active movement.

Responses to species-specific vocalizations in the auditory cortex of awake and anesthetized guinea pigs

“…The eVect of anesthesia involves the processing of acoustical information not only at the cortical level, but also in the subcortical stages of the auditory system such as the cochlear nucleus (Anderson and Young, 2004), inferior colliculus (Kuwada et al, 1989;Astl et al, 1996;Torterolo et al, 2002) or medial geniculate body (Cotillon-Williams and Edeline, 2003;Massaux et al, 2004). Therefore, the modiWcation of cortical activity can result not only from the direct eVect of an anesthetic agent on intracortical processing, but also from modiWed subcortical activity or, most likely, from a combination of subcortical and intracortical eVects.…”

Neural codes in the thalamocortical auditory system: From artificial stimuli to communication sounds

“…see Cotillon-Williams and Edeline, 2003;Massaux et al, 2004). This is particularly important here for at least two reasons.…”

Correlating Stimulus-Specific Adaptation of Cortical Neurons and Local Field Potentials in the Awake Rat

“…Response properties of A1 neurons in rodent are changed profoundly by application of Equithesin, urethane, or ketamine (Gaese and Ostwald, 2001;Cotillon-Williams and Edeline, 2003;Syka et al, 2005). Different anesthetics can exert a variety of effects on auditory cortical neurons resulting in, for example, threshold changes (Cheung et al, 2001), altered spontaneous rate (Zurita et al, 1994), or evoked oscillations (Cotillon-Williams and Edeline, 2003). This holds true not only for single neuron activity but also for evoked auditory potentials in rats (Borbély and Hall, 1970;Kisley and Gerstein, 1999;Miyazato et al, 1999).…”