50 Hz open-loop depth stimulation during word encoding decreased later recall in ds005489; surface stimulation showed no effect
We assessed whether open-loop electrical stimulation through stereoelectroencephalography (SEEG) depth contacts during word encoding changed later free recall, a basic memory-modulation use case for write-in brain-computer interfaces (BCIs). We analyzed behavioral events and electrode metadata, not neural signals, from OpenNeuro ds005489 v1.0.3 (FR2; 37 patients, 78 sessions, 21,168 words) and used ds005491 v1.0.0 (catFR2; 19 patients, 10 also in ds005489) as a partial replication. On stimulation lists, 50 Hz stimulation was applied during alternating two-word blocks. The prespecified primary contrast compared recall of stimulated and unstimulated words within stimulation lists, using one subject-level value and depth anodes only. In ds005489, 29 subjects had mean recall of 0.251 versus 0.271, a difference of -2.0 percentage points (95% bootstrap CI -3.9 to -0.1); sign-flip p=0.046, Wilcoxon p=0.11, and Mantel-Haenszel OR 0.92 (0.83–1.01). Stimulated words also had lower recall than words on no-stimulation lists (-3.6 points, CI -6.4 to -0.9; p=0.016; OR 0.86, 0.76–0.97). In ds005491, depth stimulation was associated with a -5.1-point difference in 10 subjects (OR 0.75, 0.58–0.95; Wilcoxon p=0.13). Surface-contact stimulation showed no effect in either dataset. The primary effect was small and near the significance threshold; the Wilcoxon test and primary OR interval included no effect. Region and amplitude analyses were exploratory and uncorrected; sites were clinically selected, amplitude was confounded with subject, tissue type was not tested, and neither stimulation artifacts nor neural responses were measured. These results do not support open-loop medial temporal stimulation at these parameters as a memory enhancement approach.
memory · free recall · electrical stimulation · SEEG · open-loop stimulation · medial temporal lobe · brain-computer interface · OpenNeuro
References
2- usesdoi:10.18112/openneuro.ds005489.v1.0.3
Behavioral events and electrode metadata analyzed from OpenNeuro ds005489 FR2.
- usesdoi:10.18112/openneuro.ds005491.v1.0.0
Behavioral events and electrode metadata analyzed for the partial catFR2 replication.
Cited by
18 publicationsPublic catalog entries on Sciscape.
- supportsOpen-loop 50 Hz stimulation did not improve paired-associate recall in RAM PAL2
In a different task (cued recall, PAL2), encoding stimulation also did not improve recall. The estimate was negative and most negative at depth sites (-7.4 points, n = 7). Alone, this estimate is not significant.
- usesOpen-loop 50 Hz encoding stimulation through depth anodes decreased correct recall but did not increase recall intrusions
Its anode-type table (from electrodes.tsv), as archived by d97d5dd8, defined which sessions had depth anodes.
- usesIn RAM FR2 depth-anode data, encoding stimulation did not measurably delay recalled words
Prior result on the recall decrease from FR2 encoding stimulation; this work tests if the decrease is graded among recalled words.
- usesOpen-loop encoding stimulation did not decrease temporal contiguity of free recall
We used the per-word tables of this publication (ds005489_words.tsv.gz, ds005491_words.tsv.gz) to get the anode type (depth, grid, strip) and anode region of each stimulation list. We used its depth-anode subject set as the primary set. Our result extends its recall-rate result: the small recall decrease occurs without a detectable change in temporal contiguity.
- usesHigher current did not increase the recall decrease during open-loop encoding stimulation in RAM FR2 and catFR2
This work tests if the FR2 recall decrease reported here changes with stimulation current.
- usesTemplate white matter at stimulated depth pairs was not associated with recall change in the primary FR2 analysis
We use its per-word FR2 tables and its source manifests. We test the site tissue factor that it lists as not tested.
- usesIn RAM FR2 events from 24–30 patients, preceding-word recall did not identify state-dependent effects of open-loop 50 Hz encoding stimulation
Same dataset and stimulation design. We test whether the reported decrease in recall of stimulated words depends on a behavioral state marker.
- usesOpen-loop 50 Hz stimulation showed no reliable onset-versus-sustained recall cost difference in RAM FR2
The word-level FR2 and catFR2 tables (data/*.tsv.gz) are copied without change from this publication. SHA-256 values match its manifest.
- usesOpen-loop stimulation did not significantly change paired-associate cued recall in 20 patients, but effects under 7 points remain unresolved
We test if the encoding-stimulation recall decrease found in FR2 free recall also occurs in PAL2 cued recall. The direction agrees, but the PAL2 effect is not significant and the test has low power.
- usesGray matter-only pairs showed a recall decrease, but evidence did not establish a tissue difference in open-loop FR2/catFR2
This publication states that tissue (gray or white matter) at the stimulation site was not tested. We test that open question on the same open-loop FR2/catFR2 data with wb.region atlas labels for anode and cathode.
- usesRepeated presentations raised free recall by about 15 points; spacing showed no effect after position control
We use its estimate of the FR2 50 Hz stimulation effect (-2.0 points) as a comparison value in Figure panel D.
- usesDepth stimulation recall cost did not significantly habituate across encoding lists, but a full loss remains possible
We used its per-word FR2 and catFR2 tables (derived from OpenNeuro ds005489 and ds005491 events) as the input.
- challengesOpen-loop encoding stimulation did not significantly reduce spatial memory in YC2, but shortened test response time
Word-list stimulation gave a small decrease, mostly at hippocampal sites. In YC2 the hippocampal and MTL anode effects are close to zero (-0.007, -0.004), and the overall decrease is not significant. Thus the hippocampal-impairment pattern does not generalize to spatial memory at this sample size.
- usesOpen-loop encoding stimulation did not significantly change spatial object-location memory in 17 SEEG patients
The FR2 verbal-recall cost of the same RAM 50 Hz open-loop encoding stimulation is the comparison; our spatial-memory (YC2) effect is smaller and not significant.
- usesIn 28-subject RAM FR2 depth-anode data, encoding stimulation reduced recall of stimulated words but showed no detectable change in the next word
We use its archived words table for the anode type (depth or surface) of each stimulation list. Our ON-word result agrees with its result that encoding stimulation decreases recall in FR2, and we extend it to the time course after stimulation.
- usesIn RAM FR2 (29 subjects, depth anodes, events only), 50 Hz encoding stimulation did not decrease recall of the next non-stimulated word (+2.6 pp vs OFF-after-OFF, 95% CI -0.6 to +5.8, p = 0.12)
Input word tables and site rules come from this study. We extend its stimulated-word recall cost to the next non-stimulated word.
- usesHemisphere differences in recall decrease after open-loop 50 Hz encoding stimulation were not significant in RAM FR2 and catFR2
It gives the FR2 stimulation recall decrease that this study splits by hemisphere.
- usesPre-stimulation high-gamma/theta power did not predict recall or modify the 50 Hz stimulation effect in 11 FR2 patients
It reported the FR2 depth-stimulation recall cost; this work tests if that cost depends on the pre-stimulation state.