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Dissociation of category-learning systems via brain potentials.

Morrison RG, Reber PJ, Bharani KL, Paller KA - Front Hum Neurosci (2015)

Bottom Line: Categorization accuracy was similar for the two distributions.A stimulus-locked Late Positive Complex (LPC) associated with explicit memory updating was modulated by accuracy in the RB, but not the II task.These results provide additional evidence for distinct brain mechanisms supporting RB vs. implicit II category learning and use.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, Neuroscience Institute, Loyola University Chicago Chicago, IL, USA.

ABSTRACT
Behavioral, neuropsychological, and neuroimaging evidence has suggested that categories can often be learned via either an explicit rule-based (RB) mechanism critically dependent on medial temporal and prefrontal brain regions, or via an implicit information-integration (II) mechanism relying on the basal ganglia. In this study, participants viewed sine-wave gratings (Gabor patches) that varied on two dimensions and learned to categorize them via trial-by-trial feedback. Two different stimulus distributions were used; one was intended to encourage an explicit RB process and the other an implicit II process. We monitored brain activity with scalp electroencephalography (EEG) while each participant: (1) passively observed stimuli represented of both distributions; (2) categorized stimuli from one distribution, and, 1 week later; (3) categorized stimuli from the other distribution. Categorization accuracy was similar for the two distributions. Subtractions of Event-Related Potentials (ERPs) for correct and incorrect trials were used to identify neural differences in RB and II categorization processes. We identified an occipital brain potential that was differentially modulated by categorization condition accuracy at an early latency (150-250 ms), likely reflecting the degree of holistic processing. A stimulus-locked Late Positive Complex (LPC) associated with explicit memory updating was modulated by accuracy in the RB, but not the II task. Likewise, a feedback-locked P300 ERP associated with expectancy was correlated with performance only in the RB, but not the II condition. These results provide additional evidence for distinct brain mechanisms supporting RB vs. implicit II category learning and use.

No MeSH data available.


Related in: MedlinePlus

Feedback-locked ERPs from a central cluster of electrodes (seven marked electrodes surrounding Cz; see Figure 3D for precise electrode locations) for (A) RB and (D) II category-learning conditions. Topographic maps representing mean amplitude from correct responses from 200–400 ms for (B) RB and (E) II ERPs. Scatterplots showing the relationship of accuracy to mean amplitude for correct trials for (C) RB and (F) II conditions.
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Figure 8: Feedback-locked ERPs from a central cluster of electrodes (seven marked electrodes surrounding Cz; see Figure 3D for precise electrode locations) for (A) RB and (D) II category-learning conditions. Topographic maps representing mean amplitude from correct responses from 200–400 ms for (B) RB and (E) II ERPs. Scatterplots showing the relationship of accuracy to mean amplitude for correct trials for (C) RB and (F) II conditions.

Mentions: In order to assess hypotheses about the extent to which categorization was based on explicit knowledge, we examined ERPs recorded during feedback (Figure 8). Participants interpret feedback signals as a function of their explicit expectations. P300 responses have been associated with confidence in learning with feedback (Hajcak et al., 2005). Accordingly, we expected P300 potentials to index learning in the RB but not in the II condition, given that explicit learning mechanisms are thought to dominate in the RB but not the II condition. Both Correct and Incorrect trials showed large positive potentials at approximately 300 ms with central-focused topographies (Figures 8A,B,D). A 2 (RB vs. II) by 2 (Correct vs. Incorrect) ANOVA was performed on post-feedback mean amplitudes at 200–400 ms from a cluster of seven central electrodes (Figure 3D). The analysis yielded a main effect of accuracy (F(1,11) = 43, p < 0.001, ηp2 = 0.78), but no effect of distribution type (F(1,11) = 0, p = 0.99, ηp2 = 0), and no interaction between distribution type and accuracy (F(1,11) = 0.25, p = 0.6, ηp2 = 0.02).


Dissociation of category-learning systems via brain potentials.

Morrison RG, Reber PJ, Bharani KL, Paller KA - Front Hum Neurosci (2015)

Feedback-locked ERPs from a central cluster of electrodes (seven marked electrodes surrounding Cz; see Figure 3D for precise electrode locations) for (A) RB and (D) II category-learning conditions. Topographic maps representing mean amplitude from correct responses from 200–400 ms for (B) RB and (E) II ERPs. Scatterplots showing the relationship of accuracy to mean amplitude for correct trials for (C) RB and (F) II conditions.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
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Figure 8: Feedback-locked ERPs from a central cluster of electrodes (seven marked electrodes surrounding Cz; see Figure 3D for precise electrode locations) for (A) RB and (D) II category-learning conditions. Topographic maps representing mean amplitude from correct responses from 200–400 ms for (B) RB and (E) II ERPs. Scatterplots showing the relationship of accuracy to mean amplitude for correct trials for (C) RB and (F) II conditions.
Mentions: In order to assess hypotheses about the extent to which categorization was based on explicit knowledge, we examined ERPs recorded during feedback (Figure 8). Participants interpret feedback signals as a function of their explicit expectations. P300 responses have been associated with confidence in learning with feedback (Hajcak et al., 2005). Accordingly, we expected P300 potentials to index learning in the RB but not in the II condition, given that explicit learning mechanisms are thought to dominate in the RB but not the II condition. Both Correct and Incorrect trials showed large positive potentials at approximately 300 ms with central-focused topographies (Figures 8A,B,D). A 2 (RB vs. II) by 2 (Correct vs. Incorrect) ANOVA was performed on post-feedback mean amplitudes at 200–400 ms from a cluster of seven central electrodes (Figure 3D). The analysis yielded a main effect of accuracy (F(1,11) = 43, p < 0.001, ηp2 = 0.78), but no effect of distribution type (F(1,11) = 0, p = 0.99, ηp2 = 0), and no interaction between distribution type and accuracy (F(1,11) = 0.25, p = 0.6, ηp2 = 0.02).

Bottom Line: Categorization accuracy was similar for the two distributions.A stimulus-locked Late Positive Complex (LPC) associated with explicit memory updating was modulated by accuracy in the RB, but not the II task.These results provide additional evidence for distinct brain mechanisms supporting RB vs. implicit II category learning and use.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychology, Neuroscience Institute, Loyola University Chicago Chicago, IL, USA.

ABSTRACT
Behavioral, neuropsychological, and neuroimaging evidence has suggested that categories can often be learned via either an explicit rule-based (RB) mechanism critically dependent on medial temporal and prefrontal brain regions, or via an implicit information-integration (II) mechanism relying on the basal ganglia. In this study, participants viewed sine-wave gratings (Gabor patches) that varied on two dimensions and learned to categorize them via trial-by-trial feedback. Two different stimulus distributions were used; one was intended to encourage an explicit RB process and the other an implicit II process. We monitored brain activity with scalp electroencephalography (EEG) while each participant: (1) passively observed stimuli represented of both distributions; (2) categorized stimuli from one distribution, and, 1 week later; (3) categorized stimuli from the other distribution. Categorization accuracy was similar for the two distributions. Subtractions of Event-Related Potentials (ERPs) for correct and incorrect trials were used to identify neural differences in RB and II categorization processes. We identified an occipital brain potential that was differentially modulated by categorization condition accuracy at an early latency (150-250 ms), likely reflecting the degree of holistic processing. A stimulus-locked Late Positive Complex (LPC) associated with explicit memory updating was modulated by accuracy in the RB, but not the II task. Likewise, a feedback-locked P300 ERP associated with expectancy was correlated with performance only in the RB, but not the II condition. These results provide additional evidence for distinct brain mechanisms supporting RB vs. implicit II category learning and use.

No MeSH data available.


Related in: MedlinePlus