Table 3.
Characteristics of studies included in meta-analysis
| Study | Extraction | Participant characteristics | fMRI language task(s) | LI calculation method (voxel count vs magnitude, threshold) |
|---|---|---|---|---|
| Adcock et al. (2003) | Individual participant data from article | Left & right; TLE; mostly HS & tumors; adult sample with one pediatric case (age range: 15–54y) | Phonemic fluency | Frontal ROI. Magnitude of activation in ROI |
| Appel et al. (2012) | Individual participant data from article | Left & right; TLE; mostly HS or MRI negative; adult sample (age range: 18–55y) | Auditory description decision | Frontal ROI. LI-toolbox: Voxel count/value, mean LIs determined across different thresholds using bootstrapping methods in ROIs |
| Arora et al. (2009) | Individual participant data from article | Left & right; mixed epilepsy locations; etiology not reported; adult and pediatric (age range: 12–51y). | Semantic and phonemic fluency*, visual sentence comprehension and auditory sentence comprehension | Whole brain ROI. Voxel count, threshold of t=2 across ROI (chosen out of a range of thresholds as it demonstrated the greatest stability) |
| Audrain et al. (2018) | Individual participant data from author | Left only; TLE; etiology not specified; adult sample (age range: 23–58y) | Conjunction of 4 language tasks: covert verb generation, sentence comprehension, category fluency and naming to description | Frontal ROI. LI-toolbox: Voxel count/value, mean LIs determined across different thresholds using bootstrapping methods in ROIs |
| Banjac et al. (2021) | Individual participant data from article | Left & right; TLE; etiology not specified; adult sample (age range: 19–54y) | Sentence generation | Frontal ROI. LI-toolbox: Voxel count/value, mean LIs determined across different thresholds using bootstrapping methods in ROIs |
| Banjac et al. (2022) | Individual participant data from article | Left only; TLE; etiology not specified; adult sample (age range: 23–58y). | Sentence generation | Frontal ROI. LI-toolbox: Voxel count/value mean LIs determined across different thresholds using bootstrapping methods in ROIs |
| Benjamin et al. (2017) | Individual participant data from article | Left & right; mostly TLE, 1 frontal and 1 fronto-temporal; mixed etiology; adult sample with one pediatric case (age range: 16–56y). | Conjunction of 3 lexico-semantic tasks: object naming, word reading, naming to description | Frontal + Temporal ROI. Voxel count, fixed threshold with a joint probability of p < 0.001 across ROI |
| Binder et al. (2010) | Individual participant data from article | Left only; TLE; etiology not specified; adult sample (age range: 21–69y) | Semantic decision | Frontal + temporal ROI. Voxel count, significantly activated voxels were defined as those with a task effect beta coefficient corresponding to p < 0.001 in ROIs |
| Brazdil et al. (2005) | Individual participant data from article | Left only; TLE; all HS; adult sample (age range: 19–53y) | Phonemic fluency | Frontal ROI. Voxel count in ROI, threshold unreported |
| Cano-Lopez et al. (2018) | Individual participant data from author | Left & right; mostly TLE, also frontal, parietal and occipital; mixed etiology; adult sample (age range: 18–61y) | Story comprehension | Frontal + temporal ROI. LI-toolbox: Voxel count/value, mean LIs determined across different thresholds using bootstrapping methods in ROIs |
| Carpentier et al. (2001) | Individual participant data from article | Left only: mostly TLE, also frontal and temporoparietal; mixed etiology; adult sample (age range: 24–51y) | Conjunction of syntactic and semantic judgements on auditorily and visually presentenced sentences | Frontal + temporal ROI. Voxel count, threshold of t>1.5 in ROI |
| de Ribaupierre et al. (2012) | Individual participant data from article | Left only; TLE and FLE; mostly dysplasia; pediatric sample (age range: 7–15y) | Sentence generation | Whole brain ROI. Count of voxels activated above p<0.05 and p<0.01 (FDR) in ROI |
| Everts et al. (2010) | Individual participant data from article | Left & right; frontal, temporal and other; mixed etiology; pediatric sample (age range: 7–17y) | Phonemic fluency | Frontal ROI. LI-toolbox: Voxel count/value, mean LIs determined across different thresholds using bootstrapping methods in ROIs |
| Fernandes et al. (2006) | Individual participant data from article | Left & right; frontal, temporal and other; etiology not specified; pediatric sample (age range: 10–17y) | Verb generation | Frontal ROI. Count of voxels activated above 2.25 SD of the mean for each participant. LIs were then recomputed by using the average cross-correlation value of activated voxels (using the same 2.25 SD criteria) within the same ROI |
| Genetti et al. (2013) | Individual participant data from article | Left & right; mostly temporal; etiology not specified; adult and pediatric sample (age range: 11–48y) | Auditory semantic decision task | Frontal ROI. Count of voxels activated above p < 0.05 (FWE) in ROIs |
| Gross et al. (2022) | Individual participant data from author | Left TLE; mixed etiologies; adult sample (age range: 18–68y) | Semantic decision | Frontal + temporal ROI. Voxel count/value, mean LIs determined across different thresholds using bootstrapping methods in ROIs |
| Herfurth et al. (2022) | Individual participant data from article | Left only; mostly temporal; mostly HS; adult sample (age range: 20–57y) | Verb generation | Frontal ROI. Sum of threshold surviving t-values per left and right ROI. |
| Hertz-Pannier et al. (1997) | Individual participant data from article | Left & right; mostly TLE; etiology not specified; pediatric sample (age range: 8–17y). 1 patient removed as side of epilepsy was not reported. | Phonological or semantic fluency | Frontal ROI. Count of voxels activated on a correlation coefficient map above the threshold of r=0.7 in ROI |
| Koc et al. (2020) | Individual participant data from article | Left & right; mostly TLE; mostly HS; adult sample (age range: 18–49y) | Verb generation | Frontal ROI. Count of voxels activated above p<0.05 in ROI |
| Kokkinos and Seimenis (2024) | Individual participant data from author | Left & right; TLE; some HS; adult and pediatric sample (age range: 11–52y) | Sentence generation*, reading comprehension†, listening comprehension | Frontal ROI. Count of voxels activated in the BOLD maximum (area of highest statistical change with effect) in ROIs. |
| Koop et al. (2021) | Individual participant data from article | Left only; location and etiology not specified; pediatric sample (range unknown, mean = 13y) | Conjunction of different language tasks based on age, including: rhyming, sentence completion, auditory response naming, antonym generation and word generation | Frontal + temporal ROI. Count of voxels activated above p<0.001 in ROIs |
| Miro et al. (2014) | Correlation coefficient from article | Left only; TLE; all HS; adult sample (range unknown, LH group mean = 41y, RH group mean = 45y) | Passive sentence listening | Frontal + temporal ROI. Count of voxels activated above p<0.05 (FDR) in ROI |
| Norrelgen et al. (2015) | Individual participant data from article | Left & right; TLE and some frontal and multifocal; mixed etiology; pediatric sample with two adults (age range: 8–18y). | Verb generation* and story listening | Frontal ROI. Count of voxels activated above p<0.001 in ROIs |
| Okahara et al. (2024) | Individual participant data from article | Left & right; TLE; etiology not specified; mostly adult sample with 2 children (age range: 14–62y) | Passive listening | Temporal ROI. Count of voxels activated with an extent threshold of >10 voxels. |
| Sabbah et al. (2003) | Individual participant data from article | Left & right: mostly TLE; mixed etiology; adult and pediatric sample (age range: 9–48y) | Semantic fluency | Whole brain ROI. Count of voxels activated above p<0.0001 in ROI |
| Stasenko et al. (2022) | Individual participant data from article | Left & right: TLE; mostly HS; adult sample (age range: 22–49y) | Semantic judgement | Frontal + temporal ROI. Count of voxels activated above p<0.01 in ROI |
| Sveller et al. (2006) | Correlation coefficient from article | Left TLE; mixed etiology; adult sample (range unknown, mean = 32y) | Verb generation | Frontal + temporal ROI. Count of voxels activated above p<0.001 in ROI |
| Szaflarski et al. (2008) | Individual participant data from article | Left & right; mostly TLE; mostly HS; adult sample with one child (age range: 17–53y). | Verb generation* and semantic decision/tone decision | Frontal + temporal ROI. Count of voxels with z-scores ≥ 2.58 in ROI |
| Thivard et al. (2005) | Individual participant data from article | Left & right; TLE: mostly HS; adult sample (age range: 18–55y) | Semantic fluency* and story listening | Frontal ROI. Count of voxels activated above p<0.05 (FWE) in ROIs |
| Tivarus et al. (2012) | Individual participant data from article | Left only; mostly TLE; mostly HS; adult sample (age range: 39–69y) | Conjunction of four language tasks: verb generation, semantic decision, definition naming and passive sentence reading | Frontal + temporal ROI. Count of voxels with z-scores ≥ 2.3 in ROI |
| Trimmel et al. (2019) | Individual participant data from author | Left & right; TLE; etiology not specified; adult sample (age range: 19–58y) | Phonemic fluency* and auditory naming* | Frontal ROI. Count of voxels activated above p<0.05 (FWE) in ROIs |
| van der Kallen et al. (1998) | Individual participant data from article | Left; mostly temporal; etiology not specified; adult sample (age range: 26–49y) | Verb generation | Whole brain ROI. Count of voxels activated above p<0.0001 in ROI. |
| Voets et al. (2006) | Individual participant data from article | Left only; TLE; mostly HS; mostly adult sample (age range: 15–53y) | Phonemic fluency | Frontal ROI. Activation change in voxels with maximum activation ROI |
| Wilke et al. (2011) | Individual participant data from author | Left & right; FLE and TLE; mixed etiology; pediatric sample with 2 adults (age range: 5–18y) | Expressive letter task* and receptive beep-stories task | Frontal ROI. LI toolbox: Voxel count/value, mean LIs determined across different thresholds using bootstrapping methods in ROIs |
| Yuan et al. (2006) | Individual participant data from article | Left & right; mixed location and etiology, many MRI negative; pediatric sample with 2 adults (age range: 8–19y). | Verb generation | Frontal ROI. Count of voxels activated above threshold calculated from the mean value of the t-statistics for all voxels within ROI |
| CNH sample | Additional sample | Left & right; mixed location and etiology including MRI negative; mostly pediatric sample with 17 adults (age range: 5–23y) | Auditory description decision | Frontal ROI. LI-toolbox: Voxel count/value, mean LIs determined across different thresholds using bootstrapping methods in ROIs |
| GOSH sample | Additional sample | Left & right; mixed location and etiology; pediatric sample with 1 adult (age range: 4–19y) | Verb generation | Frontal ROI. LI-toolbox: Voxel count/value, mean LIs determined across different thresholds using bootstrapping methods in ROI |
*
Indicates the language task used if multiple were reported.
†
Indicates the language task used for the temporal LI if different from the task used for the frontal LI.
fMRI = functional magnetic resonance imaging; FDR = false discovery rate; FWE = family wise error; CNH = Children’s National Medical Centre; GOSH = Great Ormond Street Hospital; HS = hippocampal sclerosis; LI = laterality index; ROI = region of interest; TLE = temporal lobe epilepsy.