Alan A. Beaton

The Relation of Planum Temporale Asymmetry and Morphology of the Corpus Callosum to Handedness, Gender, and Dyslexia: A Review of the Evidence ☆ ☆☆ ★

Asymmetry of the planum temporale in relation to handedness, gender, and dyslexia is reviewed. The frequency of rightward asymmetry is rather higher than are estimates of the proportion of right hemisphere speech representation in the general population. Conversely, the frequency of leftward asymmetry is lower than the proportion of the population with left hemisphere speech. Neuro-anatomic asymmetry may relate more to handedness than to language lateralization. There are suggestions that neuroanatomic asymmetry is reduced in females compared to males but the data are inconclusive. Reports concerning handedness and gender differences in callosal structure are conflicting but, as with planum asymmetry, any effect of handedness is as likely to relate to degree as to direction of handedness. It has been reported that the plana are more often symmetrical in size or larger on the right side among dyslexics than controls but this has not always been found. However, greater frequency of atypical (a)symmetry of the planum in dyslexia would be consistent with the absence of a factor which, when present, biases the distribution of planum asymmetry toward the left (and handedness towards the right) as hypothesized by Annett (1985). Studies of the size of the corpus callosum in dyslexia have produced conflicting findings.

Factors affecting the learning of foreign language vocabulary: Imagery keyword mediators and phonological short-term memory

In order to investigate the cognitive processes involved in learning Foreign Language (FL) vocabulary, this study evaluates different methods of instruction. It demonstrates that keyword techniques are effective for receptive learning but that repetition is a superior strategy for learning to produce the foreign word. Performance is optimal when learners combine both strategies. The nature of the keyword is crucial–-whereas imageable noun keywords promote learning, verb keywords actually impede it. A theoretical analysis of the roles of phonological short-term memory, imagery, and lexical factors in FL vocabulary learning is presented.

Consensus Paper: Language and the Cerebellum: an Ongoing Enigma

In less than three decades, the concept “cerebellar neurocognition” has evolved from a mere afterthought to an entirely new and multifaceted area of neuroscientific research. A close interplay between three main strands of contemporary neuroscience induced a substantial modification of the traditional view of the cerebellum as a mere coordinator of autonomic and somatic motor functions. Indeed, the wealth of current evidence derived from detailed neuroanatomical investigations, functional neuroimaging studies with healthy subjects and patients and in-depth neuropsychological assessment of patients with cerebellar disorders shows that the cerebellum has a cardinal role to play in affective regulation, cognitive processing, and linguistic function. Although considerable progress has been made in models of cerebellar function, controversy remains regarding the exact role of the “linguistic cerebellum” in a broad variety of nonmotor language processes. This consensus paper brings together a range of different viewpoints and opinions regarding the contribution of the cerebellum to language function. Recent developments and insights in the nonmotor modulatory role of the cerebellum in language and some related disorders will be discussed. The role of the cerebellum in speech and language perception, in motor speech planning including apraxia of speech, in verbal working memory, in phonological and semantic verbal fluency, in syntax processing, in the dynamics of language production, in reading and in writing will be addressed. In addition, the functional topography of the linguistic cerebellum and the contribution of the deep nuclei to linguistic function will be briefly discussed. As such, a framework for debate and discussion will be offered in this consensus paper.

Digit ratio (2D:4D), salivary testosterone, and handedness

The length of the index finger relative to that of the ring finger, the 2D:4D ratio, has been taken to be a marker of the amount of testosterone (T) that was present in the foetal environment (Manning, Scutt, Wilson, & Lewis-Jones, 1998). It has also been suggested (Geschwind & Galaburda, 1987) that elevated levels of foetal T are associated with left-handedness and that adult levels of circulating T might relate to foetal levels (Jamison, Meier, & Campbell, 1993). We used multiple regression analyses to investigate whether there is any relationship between either left or right hand 2D:4D ratio and handedness. We also examined whether adult levels of salivary T (or cortisol, used as a control hormone) predict digit ratio and/or handedness. Although the 2D:4D ratio of neither the left nor the right hand was related to handedness, the difference between the digit ratios of the right and left hands, DR–L, was a significant predictor of handedness and of the performance difference between the hands on a peg-moving task, supporting previous findings (Manning & Peters, 2009; Manning et al., 1998; Manning, Trivers, Thornhill, & Singh, 2000; Stoyanov, Marinov, & Pashalieva, 2009). Adult circulating T levels did not predict the digit ratio of the left or right hand; nor was there a significant relationship between concentrations of salivary T (or cortisol) and either hand preference or asymmetry in manual skill. We suggest that the association between DR–L and hand preference arises because DR–L is a correlate of sensitivity to T in the developing foetus.

Language, cognition and the cerebellum: Grappling with an enigma

The part played by the cerebellum in higher cognitive functions has been and remains something of an enigma. Schmahmann and Caplan (2006) maintain that ‘‘The traditional teaching that the cerebellum is purely a motor control device no longer appears valid, if, indeed, it ever was. There is increasing recognition that the cerebellum contributes to cognitive processing and emotional control in addition to its role in motor coordination’’ (p. 290). On the contrary, Glickstein (2006) in the same issue wrote: ‘‘Evidence for a critical role for the cerebellum in cognition or emotion remains unconvincing’’ (p. 289). Despite the fact that there is a scientific journal (The Cerebellum) devoted solely to research on the cerebellum, it appeared to us from discussion with colleagues and others that recent developments in cerebellar research are not widely known outside the field of its practioners. We felt it was appropriate (70 years on from the wellknown paper by Holmes, 1939) to bring such research to the attention of a wider audience involved in cognitive neuroscience. We are grateful to the editors of Cortex for agreeing to our suggestion to compile a special issue of the journal and to our contributors for their papers. Ina letter dated18th January, 1661 addressed to Robert Boyle, Dr. Lower, assistant to the celebrated Thomas Willis, refers to the latter’s ‘‘opinion of the use of the cerebellum for involuntary motion’’, a view subsequently published in his famous text of 1664 (translated into English in 1681). Research on animals by Luigi Rolando (1809) and Pierre Flourens (1824) in the early part of the nineteenth century subsequently confirmed that lesions of the cerebellum produce severe disturbances of co-ordinated movement. More fanciful ideas, however, were propagated by the phrenologists. Franz Joseph Gall (see Gall et al., 1838,

Retention of foreign vocabulary learned using the keyword method: a ten-year follow-up

This article assesses one individuals level of recall for foreign vocabulary learned ten years previously using the keyword method. Without any revision at all, he remembered 35% of the test words with spelling fully correct and over 50% with only very minor errors of spelling. After 10 minutes spent looking at a vocabulary list, recall increased to 65% and 76% respectively. After a period of revision lasting a further 1½ hours, recall was virtually 100%. This level of recall was maintained for at least one month. The results indicate 1) that the keyword method (as incorporated in Linkword courses) may be used to learn a large list of vocabulary; and 2) this method of learning is not inimical to retention in the long term. Some theoretical aspects of the findings are discussed.

Dyslexia and the cerebellar deficit hypothesis.

During the past decade or so, the functions of the cerebellum have come under much scrutiny. Traditionally, the cerebellum has been regarded as critically involved in various aspects of motor function (Holmes, 1917, 1939; Marr, 1969; Albus, 1971; Ito, 1986, 1993). More recently, claims have been made that the cerebellum participates in linguistic and other cognitive activity (Leiner et al., 1989, 1993; Schmahmann, 1991; De Schutter and Maex, 1996; Allen et al., 1997) including reading (Fulbright et al., 1999). Indeed, recent research suggests that the cerebellum contributes to a bewildering range of nonmotor tasks (see e.g. Akshoomoff et al., 1992; Schatz et al., 1998). On the other hand, Glickstein (1993) is sceptical of the idea that the cerebellum has a role to play in cognitive functions, believing that the case for its involvement in other than motor tasks has yet to be proved. Of course, a strict differentiation between cognitive and motor functions can not be sustained (Bloedel, 1993); most action or movement is made in the service of some end and in relation to an existing cognitive framework. The report by Finch et al. (2002, this issue) represents an original, if less than totally convincing, contribution to the literature on the putative role of the cerebellum in dyslexia. In a field that has long known controversy, the cerebellar deficit hypothesis is itself controversial. This mirrors the arguments surrounding the very concept of dyslexia. There is no clear consensus as to how dyslexia should be defined (Beaton et al., 1997) or even that such a condition exists (see Stanovich, 1994). Some consider dyslexia to be simply the tail end of a normal distribution of reading achievement (Shaywitz et al., 1992) whereas others regard dyslexia as a distinct anomaly or syndrome (Critchley, 1970; Miles, 1993; Nicolson and Fawcett, 1995). Nonetheless, few would dissent from the view that some people find learning to read and to spell unexpectedly difficult and some explanation of their difficulties has to be sought at the cognitive or biological level, depending upon one’s purpose. The most widely accepted “cognitive” theory of dyslexia is that it depends upon some impairment or weakness in phonological processing and/or in the phonological representation of words (Snowling and Hulme, 1994; Snowling, 2001). Alternative, though not necessarily incompatible, views are that dyslexia involves an auditory temporal processing deficit (Tallal, 1980, 1984) or a deficit in the automatisation of skills (Nicolson and Fawcett, 1990; Fawcett and Nicolson, 1992), including word recognition. The biological underpinnings of dyslexia are largely unknown. Recent neuroimaging studies point inter alia to some functional abnormality of language

Facilitation of receptive and productive foreign vocabulary learning using the keyword method: The role of image quality

Ellis and Beaton (1993a) reported that the keyword method of learning enhanced memory of foreign vocabulary items when receptive learning was measured. However, for productive learning, rote repetition was superior to the keyword method. The first two experiments reported here show that, in comparison with rote repetition, both receptive and productive learning can be enhanced by the keyword method, provided that the quality of the keyword images is adequate. In a third experiment using a subset of words from Ellis and Beaton (1993a), the finding they reported, that for productive learning rote repetition was superior to the keyword method, was reversed. The quality of keyword images will vary from study to study and any generalisation regarding the efficacy of the keyword method must take this into account.

Howzat?! Why is there an over-representation of left-handed bowlers in professional cricket in the UK?

An analysis of the bowling action of professional cricketers in the UK for four seasons between 1981 and 1991 shows there to be a significant association between handedness and bowling style (seam or spin bowling). Furthermore, there is a significantly higher number of left-handed spin bowlers than would be predicted from the general population, but not left-handed seam bowlers. As the technical differences between left- and right-handed orthodox spin bowlers are much greater than those between left- and right-handed seam bowlers, these data are consistent with the view that the over-representation of left-handed bowlers reported by Wood and Aggleton (1989) is due to strategic rather than neuropsychological factors.

The enigmatic linguistic cerebellum: clinical relevance and unanswered questions on nonmotor speech and language deficits in cerebellar disorders

Clinical case descriptions and experimental evidence dating back to the early part of the 19th century from time to time documented a range of nonmotor cognitive and affective impairments following cerebellar pathology. However, a causal relationship between disruption of nonmotor cognitive and affective skills and cerebellar disease was dismissed for several decades and the classical view of the cerebellum as a mere coordinator of autonomic and somatic sensorimotor function prevailed for more than two centuries in behavioural neuroscience. The ignorance of early clinical evidence suggesting a much richer and complex role for the cerebellum than a pure sensorimotor one is remarkable given that in addition: 1) the cerebellum contains more neurons than the rest of the combined cerebral cortex and 2) no other structure has as many connections with other parts of the brain as the cerebellum. During the past decades, the long-standing view of the cerebellum as pure coordinator of sensorimotor function has been substantially modified. From the late 1970s onwards, major advances were made in elucidating the many functional neuroanatomical connections of the cerebellum with the supratentorial association cortices that subserve nonmotor language, cognition and affect. Combined with evidence derived from experimental functional neuroimaging studies in healthy subjects and neurophysiological and neuropsychological research in patients, the role of the cerebellum has been substantially extended to include that of a crucial modulator of cognitive and affective processes. In addition to its long-established role in coordinating motor aspects of speech production, clinical and experimental studies with patients suffering from etiologically different cerebellar disorders have identified involvement of the cerebellum in a variety of nonmotor language functions, including motor speech planning, language dynamics and verbal fluency, phonological and semantic word retrieval, expressive and receptive syntax processing, various aspects of reading and writing and aphasia-like phenomena. Despite considerable efforts currently devoted to further refine typology and anatomoclinical configurations of nonmotor linguistic dysfunctions linked to cerebellar pathology, the exact underlying pathophysiological mechanisms of cerebellar involvement remain to be elucidated.