Neurophysics of temporal discrimination in the rat: A mismatch negativity study

Abstract

Behavioral estimates of time discrimination threshold on animals might be contaminated by the conditioning procedure used and by attentional effects. To avoid such side effects, we measured time discrimination by recording the rat electroencephalographic response to small temporal variations. Freely moving rats were presented with repetitive sounds, some of them being occasionally shorter than the standard, to produce a Mismatch Negativity (MMN) which is known to primarily involve preattentive processes. The smallest difference eliciting a MMN located the discrimination threshold between 16% and 33% of the standard, without attentional confound. Being observed in several species, MMN can be used to decipher both the phylogenetic and ontogenetic evolution of time discrimination, without attentional confound.

Epidural Auditory Event-Related Potentials in the Rat to Frequency and duration Deviants: Evidence of Mismatch Negativity?

“…Our duration deviant data are comparable, in one respect, with the only published paper reporting duration MMN data in rats (Roger et al, 2009) in that MMN-like activity appeared as a negative displacement of deviant relative to the standard ERP, although in our study only the LD deviant showed significant evidence of an MMN-like response. However, some caution is warranted in interpreting these data as evidence of MMN-like activity, since the late negative displacements in deviant ERPs were insensitive to the degree of preceding stimulus regularity.…”

“…For the duration oddball blocks, two durations, short duration (SD) of 50 ms and a long duration (LD) of 150 ms, were used (both 3000 Hz) based on the observation by Roger et al (2009) that these durations resulted in robust MMN-like activity in the rat in a descending sequence. In the ascending oddball sequence, the SD and LD tones were the ST and DEV respectively.…”

“…These include whether MMN-like activity is measured using single/multiunit activity (MUA) and evoked local field potentials (eLFPs; von der Behrens et al, 2009; Farley et al, 2010) or from epidural sites (see Table 1), and whether controls for the physical characteristics of standard and deviant stimuli and recent stimulus history have been implemented. Similarly, the use of anesthesia during recordings makes interpretation of results problematic since anesthetics alter the physiological properties of neural elements underlying MMN activity (Roger et al, 2009). Only two of the nine previous MMN studies using epidural recordings in the rat (see Table 1) used awake (unanesthetized) animals.…”

Criteria for determining whether mismatch responses exist in animal models: Focus on rodents

“…Recordings made under anaesthesia, whether it be via urethane, isoflurane or pentobarbital sodium, tend to report ERPs with a large, single positive peak, that exhibits a positive shift in response to the deviant (Ahmed et al, 2011;Astikainen et al, 2014;Astikainen et al, 2006;Astikainen et al, 2011;Jung et al, 2013;Nakamura et al, 2011;Ruusuvirta et al, 2015;Tikhonravov et al, 2008Tikhonravov et al, , 2010, whereas studies using awake recordings report a more complex ERP morphology with a combination of negative and positive peaks. Of such studies using awake recordings, some report that the deviant induces negative shifts in the ERP (Cabungcal et al, 2013;Nakamura et al, 2011;Roger et al, 2009;Sivarao et al, 2014;Witten et al, 2014), but at least one other studyreports both negative and positive shifts, depending on the component (Harms et al, 2014). While positive shifts in ERPs to deviant stimuli are not necessarily consistent with human MMN, it is important to note that many of the studies that report such positive shifts have employed appropriate controls for adaptation (Ahmed et al, 2011;Astikainen et al, 2014;Astikainen et al, 2006;Astikainen et al, 2011;Jung et al, 2013;Nakamura et al, 2011;Tikhonravov et al, 2008Tikhonravov et al, , 2010, indicating that they have already met one of the more stringent criteria for determining whether a response is a human-like MMR.…”

Duration estimation entails predicting when

“…The elicitation of MMN/F by duration oddballs reported in human adults (Joutsiniemi et al, 1998;Kaukoranta et al, 1989;Näätänen et al, 1989;Tervaniemi et al, 1999), children (Kushnerenko et al, 2001) and rats (Roger et al, 2009) suggests that temporal information can be automatically encoded and thus, that an internal template for duration is possible. In a seminal report, the existence of an MMN elicited by duration changes was taken as supporting evidence for a memory trace and for the possible existence of duration neurons in auditory cortex .…”