Article Figures & Data
Figures
- Figure 1.
Experimental design. Participants performed the identification (Id) and discrimination (Di) tasks with two continua before and after a 15 min rTMS train. Stimuli from /ba/–/da/ and /ka/–/ga/ continua were used in experiment 1 and from /pa/–/ta/ and /da/–/ga/ continua in experiment 2. Baseline MEPs were recorded in the middle of the pre-rTMS condition. Post-rTMS MEPs were recorded in the middle and at the end of the post-rTMS condition.
- Figure 2.
Effect of rTMS on cortical excitability. The graph presents mean (±SE) peak-to-peak amplitudes of post-rTMS MEPs in relation to pre-rTMS MEPs. In experiments 1a and 2, rTMS was applied over the lip area of left M1 and MEPs were recorded from the lip muscle. In experiment 1b, rTMS was applied over the hand representation and MEPs were recorded from the hand muscle. The post-rTMS MEPs were recorded ∼7 min (Post1) and 15 min (Post2) after the end of the 15 min low-frequency rTMS train.
- Figure 3.
Performance of a participant on CP tasks. A, Identification. The graph shows typical performance in a pre-rTMS identification task, demonstrating categorical perception. The circles show proportions of /ba/ responses to each stimulus along the eight-step /ba/–/da/ continuum. A logistic curve was fit to these data points (solid line). The position of the category boundary is at 4.2 along the /ba/–/da/ continuum (see arrow). B, Discrimination. The graph shows typical performance in a pre-rTMS discrimination task, in which the participant was presented with two stimuli and asked to indicate whether they were the same or different. The proportions of different responses are plotted. In this participant, the pair of stimuli 3 and 5 and the pair stimuli 4 and 6 were across-category pairs (black bars).
- Figure 4.
Effect of rTMS on categorical perception. A, Changes in the slopes of the category boundaries. The graph presents mean (±SE) differences between conditions (post-rTMS–pre-rTMS) in the slope indices derived from the logistic curves fit to each participant's identification data. B, Changes in the proportions of across-category pairs perceived as different. The graph presents mean (±SE) differences between conditions (post-rTMS–pre-rTMS) in the proportions of different responses to individually defined across-category pairs. *p < 0.05, **p < 0.01, ***p < 0.001.
Tables
- Table 1.
Identification task: Mean slopes and positions of category boundaries in pre- and post-rTMS conditions (±SE)
Slopes Positions Pre Post Pre Post Lip (experiment 1a) /ba/–/da/ 0.92 (0.06) 0.80 (0.08) 4.31 (0.28) 4.14 (0.42) /ka/–/ga/ 0.81 (0.07) 0.93 (0.07) 4.31 (0.19) 4.44 (0.13) Hand (experiment 1b) /ba/–/da/ 0.87 (0.06) 0.91 (0.05) 4.28 (0.25) 4.30 (0.18) /ka/–/ga/ 0.94 (0.09) 0.86 (0.07) 4.31 (0.04) 4.45 (0.14) Lip (experiment 2) /pa/–/ta/ 0.86 (0.07) 0.88 (0.07) 4.84 (0.25) 4.75 (0.15) /da/–/ga/ 0.68 (0.06) 0.78 (0.08) 4.04 (0.39) 3.84 (0.26) -
Logistic curves were fit to the identification data to estimate slopes and positions of category boundaries. Bold indicates significant change from pre- to post-rTMS condition (p < 0.05).
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- Table 2.
Discrimination task: Mean proportions of different responses to across- and within-category pairs in pre- and post-rTMS conditions (±SE)
Across-category Within-category Pre Post Pre Post Lip (experiment 1a) /ba/–/da/ 0.73 (0.11) 0.58 (0.10) 0.20 (0.08) 0.24 (0.10) /ka/–/ga/ 0.78 (0.11) 0.84 (0.05) 0.08 (0.02) 0.12 (0.03) Hand (experiment 1b) /ba/–/da/ 0.71 (0.10) 0.76 (0.08) 0.16 (0.03) 0.10 (0.05) /ka/–/ga/ 0.78 (0.06) 0.71 (0.06) 0.11 (0.04) 0.13 (0.04) Lip (experiment 2) /pa/–/ta/ 0.70 (0.07) 0.53 (0.10) 0.12 (0.04) 0.10 (0.03) /da/–/ga/ 0.62 (0.08) 0.65 (0.08) 0.19 (0.06) 0.15 (0.04) -
The proportion of different responses provides a measure of discriminability of stimuli. The across-category stimuli were discriminated more accurately than within-category stimuli. Bold indicates significant change from pre- to post-rTMS condition (p < 0.01).
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