Learning of sensory sequences in cerebellar patients

Abstract

A possible role of the cerebellum in detecting and recognizing event sequences has been proposed. The present study sought to determine whether patients with cerebellar lesions are impaired in the acquisition and discrimination of sequences of sensory stimuli of different modalities. A group of 26 cerebellar patients and 26 controls matched for age, sex, handedness, musicality, and level of education were tested. Auditory and visual sensory sequences were presented out of different sensory pattern categories (tones with different acoustic frequencies and durations, visual stimuli with different spatial locations and colors, sequential vision of irregular shapes) and different ranges of inter-cue time intervals (fast and slow). Motor requirements were small, with vocal responses and no time restrictions. Perception of visual and acoustic stimuli was generally preserved in patients and controls. The number of errors was significantly higher in the faster tempo of sequence presentation in learning of sequences of tones of different frequencies and in learning of sequences of visual stimuli of different spatial locations and different colors. No difference in tempo between the groups was shown. The total number of errors between the two groups was identical in the sequence conditions. No major disturbances in acquisition or discrimination of various sensory sequences were observed in the group of cerebellar patients. Sequence learning may be impaired only in tasks with significant motor demands.

Figure 1

Test and control conditions of paradigms 1 and 2 (learning of sequences of acoustic tones).

Figure 2

Test and control conditions of paradigms 3, 4, and 5 (learning of sequences of simple visual images).

Figure 3

Three sets of shapes used in paradigm 5 (learning of templates by sequential vision). The first line shows the shapes of the condition sequential vision of lines (VL). The second line shows the shapes of the condition sequential vision of dots (VD). The third line shows the shapes of the control condition complete vision (VC). Shape 1 of each set of shapes was the reference shape; the others were test shapes.

Figure 4

Learning of sequences of acoustic tones. (A) Learning of sequences of tones of different frequencies with a slower tempo of successive tones (FS), faster tempo (FF), and the control condition (discrimination of tone frequencies, FC). Error rate per block (1-4) for all cerebellar patients (n = 26) and control subjects (n = 26). Error bars indicate the standard deviation. (B) Learning of sequences of tones of different durations (n = 12) with a slower tempo of successive tones (DS), faster tempo (DF), and the two control conditions [discrimination of long (DSC) and short (DFC) tone durations].

Figure 5

Learning of sequences of simple visual images. (A) Learning of sequences of visual stimuli of different spatial locations (n = 12) with a slower tempo (LS), faster tempo (LF), and the control condition (discrimination of spatial locations, LC). (B) Learning of sequences of different colors (n = 12) with a slower tempo (CS), faster tempo (CF), and the control condition (discrimination of different colors, CC). (C) Learning of templates by sequential vision (n = 14) with sequential vision of line segments (VL), sequential vision of single dots (VD), and the control condition (complete vision, VC).