Table 5.
Performance evaluation of the NSR system on the stimuli within the Gump set using three different types of feature vectors (MFCCs, HGSs, and HGWs) across four different subject sets (the three individual subjects and one combination of all subjects). Both single-trial and averaged neural response feature vectors were evaluated. Chance performance, which involves predicting the most likely phoneme /s/ at each time point, is also included. The phoneme error rate, posteriogram accuracy, and confusion accuracy metrics are used to assess the estimation and decoding results. All results are given as percentages in the following form: mean ± standard deviation.
| Feature set
|
Results
|
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|---|---|---|---|---|---|---|---|
| Estimation
|
Decoding
|
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| Feature type | Subject(s) | Phoneme error rate (%) | Posteriogram accuracy (%) | Confusion accuracy (%) | Phoneme error rate (%) | Posteriogram accuracy (%) | Confusion accuracy (%) |
| Chance | − | 97.12 ± 5.34 | 7.06 ± 9.77 | 2.63 ± 16.01 | 97.12 ± 5.34 | 7.06 ± 9.77 | 2.63 ± 16.01 |
| MFCC | − | 208.16 ± 67.45 | 40.45 ± 10.76 | 34.51 ± 16.15 | 60.60 ± 25.16 | 41.88 ± 17.30 | 36.30 ± 10.86 |
| Single-trial HGS | A | 188.73 ± 90.28 | 11.74 ± 7.98 | 7.67 ± 10.03 | 90.84 ± 25.00 | 11.79 ± 10.88 | 11.49 ± 7.94 |
| B | 176.91 ± 114.31 | 7.72 ± 6.02 | 4.79 ± 4.96 | 92.31 ± 26.43 | 10.23 ± 11.06 | 9.63 ± 5.52 | |
| C | 173.83 ± 92.48 | 9.00 ± 6.76 | 4.80 ± 7.22 | 87.67 ± 17.36 | 10.70 ± 11.58 | 8.16 ± 6.23 | |
| Single-trial HGW | A | 169.68 ± 84.89 | 15.62 ± 9.21 | 12.76 ± 10.12 | 86.34 ± 22.07 | 15.06 ± 11.73 | 14.89 ± 9.01 |
| B | 151.70 ± 78.01 | 12.69 ± 8.18 | 9.58 ± 5.89 | 90.63 ± 26.28 | 12.71 ± 11.49 | 11.80 ± 5.96 | |
| C | 152.48 ± 75.98 | 12.93 ± 8.77 | 8.09 ± 8.22 | 85.71 ± 17.30 | 12.62 ± 12.10 | 9.84 ± 6.40 | |
| Averaged HGS | A | 182.53 ± 89.81 | 14.68 ± 8.87 | 10.81 ± 10.80 | 86.37 ± 20.83 | 14.03 ± 11.72 | 14.07 ± 9.28 |
| B | 182.80 ± 99.75 | 11.95 ± 7.82 | 8.21 ± 6.92 | 87.13 ± 18.01 | 13.51 ± 11.30 | 12.59 ± 7.26 | |
| C | 181.75 ± 78.74 | 12.22 ± 8.01 | 7.08 ± 9.01 | 85.36 ± 13.67 | 12.41 ± 11.45 | 10.01 ± 6.56 | |
| All | 180.87 ± 84.47 | 22.34 ± 9.94 | 18.14 ± 10.47 | 76.68 ± 15.82 | 23.41 ± 13.85 | 21.39 ± 9.12 | |
| Averaged HGW | A | 158.00 ± 69.86 | 18.93 ± 10.39 | 16.49 ± 10.99 | 81.39 ± 18.85 | 18.79 ± 12.57 | 18.49 ± 10.30 |
| B | 149.66 ± 65.27 | 17.35 ± 9.46 | 13.80 ± 7.30 | 82.84 ± 21.02 | 17.64 ± 13.31 | 15.30 ± 6.99 | |
| C | 157.35 ± 73.80 | 16.42 ± 9.84 | 11.20 ± 8.79 | 83.65 ± 19.18 | 15.36 ± 13.02 | 12.27 ± 7.99 | |
| All | 142.96 ± 61.31 | 28.36 ± 10.47 | 24.02 ± 10.99 | 70.47 ± 16.77 | 29.26 ± 14.88 | 25.03 ± 10.69 | |