A PET investigation of implicit and explicit sequence learning

Abstract

Abstract:The purpose of this study was to determine the mediating neuroanatomy of implicit and explicit sequence learning using a modified version of the serial reaction time (SRT) paradigm. Subjects were seven healthy, right-handed adults (three male, four female, mean age 26.7, range 1843 yr). PET data were acquired via the oxygen-15-labeled-carbon dioxide inhalation method while subjects performed the SRT. Subjects were scanned during two blocks each of I) no sequence (Random), 2 ) single-blind, 12-item sequence (Implicit), and 3) unblinded, same sequence (Explicit). Whole-brain-normalized images reflecting relative regional cerebral blood flow (rCBF) were transformed to Talairach space, and statistical parametric maps (SPMs) of z-scores were generated for comparisons of interest. The threshold for significant activation was defined as z-score 2 3.00. Behavioral data demonstrated significant learning (P < .05) for Implicit and Explicit conditions. Tests of explicit knowledge reflected non-significant explicit contamination during the Implicit condition. Foci of significant activation in the Implicit condition were found in right ventral premotor cortex, right ventral caudate/nucleus accumbens, right thalamus, and bilateral area 19; activation in the Explicit condition included primary visual cortex, peri-sylvian cortex, and cerebellar vermis. Activations in visual and language areas during the Explicit condition may reflect conscious learning strategies including covert verbal rehearsal and visual imagery. Right-sided premotor, striatal, and thalamic activations support the notion that implicit sequence learning is mediated by cortico-striatal pathways, preferentially within the right hemisphere. o 1996 Wiky-Liss, h e .

What is the impact of the explicit knowledge of sequence regularities on both deterministic and probabilistic serial reaction time task performance?

“…Our study is also supported by the findings of Rauch et al (1995), who showed that the neuronal correlates of explicit and implicit learning were different. In this context, we might hypothesize that the primary visual and inferior parietal cortices (which are specific to explicit learning) would not have been involved in the participants' performance in Experiment 2, neither in the incidental-learning nor in the explicit-learning condition; indeed, as we have shown, the participants in the explicit-learning conditions could not use the explicitly learned information.…”

“…They concluded that learning a probabilistic sequence depends essentially on implicit-learning mechanisms. Rauch et al (1995) also showed in a PET study that the cerebral structures activated when the sequence is learned explicitly differ from those activated when the sequence is learned incidentally. According to this study, the regions involved in the incidental-learning condition are the right ventral premotor cortex, the right ventral caudate/nucleus accumbens, the right thalamus, and the bilateral Area 19; in the explicit-learning condition, the areas known to play a role in visual and language processes are involved (i.e., the primary visual and inferior parietal cortex).…”

Functional Dissociation of Hippocampal Mechanism during Implicit Learning Based on the Domain of Associations

“…The results of the motor sequence group show that it is not implicit learning in general that recruits MTL structures, but only those related to perceptual learning. In contrast, motor sequence learning involved the basal ganglia and motor cortex, which has previously been reported in SRT paradigms (Grafton et al, 1995;Rauch et al, 1995;Berns et al, 1997;Hazeltine et al, 1997;Peigneux et al, 2000;Willingham et al, 2002).…”

“…Neuroimaging studies reported controversial results regarding the participation of MTL structures during SRT learning. Most studies observed activation in the putamen and the striatum (Grafton et al, 1995;Rauch et al, 1995;Berns et al, 1997;Hazeltine et al, 1997;Peigneux et al, 2000;Willingham et al, 2002). However, a recent study demonstrated MTL activation during implicit and explicit SRT learning (Schendan et al, 2003).…”

Learned material content and acquisition level modulate cerebral reactivation during posttraining rapid-eye-movements sleep

“…However, it is not commonly seen as a critical component of sequence learning. In contrast, the striatum is known to participate in implicit sequence learning (Grafton et al, 1995;Rauch et al, 1995;Rauch et al, 1997) and specifically in the encoding of the temporal context set by the previous stimulus in the probabilistic SRT task . The finding that the strength of the functional connections between cuneus and striatum is increased during post-training REM sleep suggests the involvement of the basal ganglia in the off-line reprocessing of implicitly acquired high-order sequential information.…”