No strong evidence for lateralisation of word reading and face recognition deficits following posterior brain injury

Abstract

Face recognition and word reading are thought to be mediated by relatively independent cognitive systems lateralised to the right and left hemispheres, respectively. In this case, we should expect a higher incidence of face recognition problems in patients with right hemisphere injury and a higher incidence of reading problems in patients with left hemisphere injury. We tested this hypothesis in a group of 31 patients with unilateral right or left hemisphere infarcts in the territory of the posterior cerebral arteries. In most domains tested (e.g., visual attention, object recognition, visuo-construction, motion perception), we found that both patient groups performed significantly worse than a matched control group. In particular, we found a significant number of face recognition deficits in patients with left hemisphere injury and a significant number of patients with word reading deficits following right hemisphere injury. This suggests that face recognition and word reading may be mediated by more bilaterally distributed neural systems than is commonly assumed.

Keywords:

• Face recognition
• Lateralisation
• Object recognition
• PCA stroke
• Word reading

We acknowledge the contributions by Glyn Humphreys and Hanne Udesen in the planning stages of this research, not to mention the always inspiring presence of F. F. Fakutsi.

We acknowledge the contributions by Glyn Humphreys and Hanne Udesen in the planning stages of this research, not to mention the always inspiring presence of F. F. Fakutsi.

Supplementary material

Supplementary Table is available via the “Supplementary” tab on the article's online page (http://dx.doi.org/10.1080/20445911.2014.928713).

Notes

¹ Martinaud et al. (2012) analysed their data a little differently than we analysed our data. Martinaud et al. considered patients impaired if their score fell 2 SDs below the mean of the control sample (two-tailed statistics). On the plausible assumption that patients will perform worse and not better relative to controls, we instead based our comparisons on one-tailed statistics. If we re-analyse the data reported by Martinaud et al. using our approach—as is done later—we find that also in the study by Martinaud et al.: (1) Some impairment in reading is seen in patients with unilateral right hemisphere injury, (2) some impairment in face recognition is seen following unilateral left hemisphere injury and (3) the difference between unilateral right and left infarct patients in terms of reading and face recognition deficits is not significant.

Of the right unilateral infarct patients reported in the study by Martinaud et al. (2012), one had impaired reading in terms of accuracy (No. 25) [falling one percent-point below the worst performance of the control group] whereas five (Nos. 21, 24, 25, 26 and 28) had a word-length effect that was significantly longer than that of the control sample (p < .05, one-tailed: Crawford & Garthwaite, 2002). In comparison, 3 out of the 15 left infarct patients were impaired in terms of accuracy (Nos. 8, 9 and 12) whereas 10 (Nos. 1, 3, 6, 8, 9, 11, 12, 13, 14 and 15) showed an abnormal word-length effect (p < .05, one-tailed: Crawford & Garthwaite, 2002). In terms of frequency there is no significant difference between the left and right infarct groups in accuracy (χ² exact significance = 0.86, p = .6) nor in word-length effect (χ² exact significance = 0.08, p = 1).

On their old/new face discrimination task two patients with unilateral left hemisphere injury (Nos. 2 and 12) performed significantly worse than the control subjects (p < .05, one-tailed: Crawford & Garthwaite, 2002). In comparison the same is found for five patients with unilateral right hemisphere injury (Nos. 20, 21, 22, 25 and 26) (p < .05, one-tailed: Crawford & Garthwaite, 2002). Again, the difference between left and right infarct patients in frequency of face discrimination problems is not statistically significant (χ² exact significance = 2.79, p = .19).

Martinaud et al. also examined performance on the Cambridge Face Memory test for their left and right infarct patients and found no significant difference in frequency of impairment on this task (two left vs. three right infarct patients). Adopting our criterion for impaired performance does not change this overall result: three patients with left hemisphere injury (Nos. 8, 10 and 12) vs. four patients with right hemisphere injury (Nos. 22, 25, 26 and 27); a difference that is not significant (χ² exact significance = .43, p = .67).