Matthew Lambon-Ralph

Dept. of Psychology,
University of Manchester,
Oxford Road, Manchester






Selected references below

Lambon-Ralph, M. A., Hesketh, A., & Sage, K. (2004). Implicit recognition in pure alexia: The Saffran effect - A tale of two systems or two procedures? Cognitive Neuropsychology, 21, 401-421.
Notes: Prof. M.A. Lambon Ralph, Dept. of Psychology, University of Manchester, Oxford Road, Manchester M13 9PL
Some patients with pure alexia or letter-by-letter reading demonstrate the Saffran effect: residual activation of higher order lexical-semantic representations despite poor word recognition. This study investigated the reading of patient FD, a letter-by-letter reader with a clear Saffran effect. Two alternative explanations for this effect were tested in a series of experiments and through the impact of whole-word and letter-based therapies on FD's reading. One theory assumes that the disparity between overt recognition and implicit activation of word meaning is underpinned by two separate reading systems. An alternative hypothesis argues for a single whole-word reading system supplemented by the deliberate, compensatory strategy of letter-by-letter reading. Under this hypothesis, the Saffran effect reflects partial activation of the single, whole-word system. FD's results strongly supported the latter hypothesis. FD's reading behaviour was characterised by partial activation of higher word representations, accuracy was graded by word variables known to influence the normal reading system, and most importantly, once the characteristics of the tasks were equated, there was no evidence for a dissociation between word categorisation and recognition. In addition, the whole-word therapy encouraged FD to abandon the letter-by-letter strategy. Without this compensatory technique, FD's emergent deep dyslexia was consistent with a partially activated, whole-word reading system that produces overt reading responses. Comparison of data from this and other studies suggests that the Saffran effect is most likely to be observed in patients with severe pure alexia.

Mechelli, A., Crinion, J. T., Long, S., Friston, K. J., Lambon-Ralph, M. A., Patterson, K. et al. (2005). Dissociating reading processes on the basis of neuronal interactions. Journal of Cognitive Neuroscience, 17, 1753-1765.
Notes: Functional Imaging Laboratory, Wellcome Department of Imaging Neuroscience, Institute of Neurology, London, UK.
Previous studies of patients with phonological and surface alexia have demonstrated a double dissociation between the reading of pseudo words and words with atypical spelling-to-sound relationships. A corresponding double dissociation in the neuronal activation patterns for pseudo words and exception words has not, however, been consistently demonstrated in normal subjects. Motivated by the literature on acquired alexia, the present study contrasted pseudo words to exception words and explored how neuronal interactions within the reading system are influenced by word type. Functional magnetic resonance imaging was used to measure neuronal responses during reading in 22 healthy volunteers. The direct comparison of reading pseudo words and exception words revealed a double dissociation within the left frontal cortex. Pseudo words preferentially increased left dorsal premotor activation, whereas exception words preferentially increased left pars triangularis activation. Critically, these areas correspond to those previously associated with phonological and semantic processing, respectively. Word-type dependent interactions between brain areas were then investigated using dynamic causal modeling. This revealed that increased activation in the dorsal premotor cortex for pseudo words was associated with a selective increase in effective connectivity from the posterior fusiform gyrus. In contrast, increased activation in the pars triangularis for exception words was associated with a selective increase in effective connectivity from the anterior fusiform gyrus. The present investigation is the first to identify distinct neuronal mechanisms for semantic and phonological contributions to reading

Roberts, D. J., Lambon Ralph, M. A., & Woollams, A. M. (2010). When does less yield more? The impact of severity upon implicit recognition in pure alexia. Neuropsychologia, 48, 2437-2446.
Notes: Pure alexia (PA) is characterised by strong effects of word length on reading times and is sometimes accompanied by an overt letter-by-letter (LBL) reading strategy. Past studies have reported "implicit recognition" in some individual PA patients. This is a striking finding because such patients are able to perform semantic classification and lexical decision at above chance levels even when the exposure duration is short enough to prevent explicit identification. In an attempt to determine the prevalence of this "implicit recognition" effect, we assessed semantic categorisation and lexical decision performance using limited exposure durations in 10 PA cases. The majority of the patients showed above chance accuracy in semantic categorisation and lexical decision. Performance on the lexical decision test was influenced by frequency and imageability. In addition, we found that the extent to which patients showed evidence of "implicit recognition" in both tasks was inversely related to the severity of their reading disorder. This result is consistent with hypotheses which suggest that this effect does not constitute an implicit form of unique word identification but is a reflection of the degree of partial activation within the word recognition system. These results also go some way towards explaining the individual variation in the presence of this effect observed across previous case-study investigations in the literature
Neuroscience and Aphasia Research Unit, School of Psychological Sciences, University of Manchester, Manchester, UK

Roberts, D. J., Woollams, A. M., Kim, E., Beeson, P. M., Rapcsak, S. Z., & Lambon Ralph, M. A. (2012). Efficient Visual Object and Word Recognition Relies on High Spatial Frequency Coding in the Left Posterior Fusiform Gyrus: Evidence from a Case-Series of Patients with Ventral Occipito-Temporal Cortex Damage. Cerebral Cortex.
Notes: Recent visual neuroscience investigations suggest that ventral occipito-temporal cortex is retinotopically organized, with high acuity foveal input projecting primarily to the posterior fusiform gyrus (pFG), making this region crucial for coding high spatial frequency information. Because high spatial frequencies are critical for fine-grained visual discrimination, we hypothesized that damage to the left pFG should have an adverse effect not only on efficient reading, as observed in pure alexia, but also on the processing of complex non-orthographic visual stimuli. Consistent with this hypothesis, we obtained evidence that a large case series (n = 20) of patients with lesions centered on left pFG: 1) Exhibited reduced sensitivity to high spatial frequencies; 2) demonstrated prolonged response latencies both in reading (pure alexia) and object naming; and 3) were especially sensitive to visual complexity and similarity when discriminating between novel visual patterns. These results suggest that the patients' dual reading and non-orthographic recognition impairments have a common underlying mechanism and reflect the loss of high spatial frequency visual information normally coded in the left pFG
Neuroscience and Aphasia Research Unit, School of Psychological Sciences, University of Manchester, Manchester, UK

Anders Gade