Sentence repetition and processing resources in Alzheimer's disease

Sentence processing in Alzheimer's disease (AD) has been found to be influenced by several grammatical and extragrammatical factors, including phrase structure and verb-argument relations, number of propositions/verbs, and processing resource capacity. This study examines the effects of these variables on sentence production in AD. Normal control and AD subjects were asked to repeat six types of sentences varying along the above dimensions of complexity. Subjects' processing resource capacity was measured using several verbal working memory tests. AD subjects' sentence-repetition performance was impaired compared to the normal control group. Significant effects were observed for branching direction of phrase structure, canonicity of verb-argument relations, and serial position of errors. Sentence-repetition performance significantly correlated with working memory scores. The findings are interpreted within a resource capacity theory of sentence processing.     

Effects of directionality in deductive reasoning: I. The comprehension of single relational premises

Four experiments involving 123 university students tested directionality effects in the comprehension of spatial relations, quantified statements, and propositional connectives with a sentence-picture verification task. Presentation of the referents of terms in the statements was separated by 1 s, and presentation order was congruent or incongruent with the order of terms in the statement. Some relations showed faster verification times for congruent display order, others for incongruent display order, and still others showed no directionality effect. The authors proposed a 2-step process model for the construction of semantic representations of relational statements, in which a reference object is established first, and then the second object is attached in relation to it. This theory explains the various directionality effects as a general preference to process information about the reference object before information about the target object.     

The generic viewpoint assumption and Bayesian inference

The task of human vision is to reliably infer useful information about the external environment from images formed on the retinae. In general, the inference of scene properties from retinal images is not deductive; it requires knowledge about the external environment. Further, it has been suggested that the environment must be regular in some way in order for any scene properties to be reliably inferred. In particular, Knill and Kersten [1991, in Pattern Recognition by Man and Machine Ed. R J Watt (London: Macmillan)] and Jepson et al [1996, in Bayesian Approaches to Perception Eds D Knill, W Richards (Cambridge: Cambridge University Press)] claim that, given an 'unbiased' prior probability distribution for the scenes being observed, the generic viewpoint assumption is not probabilistically valid. However, this claim depends upon the use of representation spaces that may not be appropriate for the problems they consider. In fact, it is problematic to define a rigorous criterion for a probability distribution to be considered 'random' or 'regularity-free' in many natural domains of interest. This problem is closely related to Bertrand's paradox. I propose that, in the case of 'unbiased' priors, the reliability of inferences based on the generic viewpoint assumption depends partly on whether or not an observed coincidence in the image involves features known to be on the same object. This proposal is based on important differences between the distributions associated with: (i) a 'random' placement of features in 3-D, and (ii) the positions of features on a 'randomly shaped' and 'randomly posed' 3-D object. Similar considerations arise in the case of inferring 3-D motion from image motion.     

The role of attention in motion extrapolation: are moving objects 'corrected' or flashed objects attentionally delayed?

Objects flashed in alignment with moving objects appear to lag behind [Nijhawan, 1994 Nature (London) 370 256-257]. Could this 'flash-lag' effect be due to attentional delays in bringing flashed items to perceptual awareness [Titchener, 1908/1973 Lectures on the Elementary Psychology of Feeling and Attention first published 1908 (New York: Macmillan); reprinted 1973 (New York: Arno Press)]? We overtly manipulated attentional allocation in three experiments to address the following questions: Is the flash-lag effect affected when attention is (a) focused on a single event in the presence of multiple events, (b) distributed over multiple events, and (c) diverted from the flashed object? To address the first two questions, five rings, moving along a circular path, were presented while observers attentively tracked one or multiple rings under four conditions: the ring in which the disk was flashed was (i) known or (ii) unknown (randomly selected from the set of five); location of the flashed disk was (i) known or (ii) unknown (randomly selected from ten locations). The third question was investigated by using two moving objects in a cost-benefit cueing paradigm. An arrow cued, with 70% or 80% validity, the position of the flashed object. Observers performed two tasks: (a) reacted as quickly as possible to flash onset; (b) reported the flash-lag effect. We obtained a significant and unaltered flash-lag effect under all the attentional conditions we employed. Furthermore, though reaction times were significantly shorter for validly cued flashes, the flash-lag effect remained uninfluenced by cue validity, indicating that quicker responses to validly cued locations may be due to the shortening of post-perceptual delays in motor responses rather than the perceptual facilitation. We conclude that the computations that give rise to the flash-lag effect are independent of attentional deployment.     

Task demands and limb apraxia in stroke

The present study was designed to examine the frequency and severity of apraxia in patients with left- or right-hemisphere stroke in both pantomime and imitation conditions and to compare the frequency of apraxia in each stroke group across the three patterns of apraxia described in Roy's model (Roy, 1996). Ninety-nine stroke patients and 15 age-matched healthy adults performed eight transitive gestures to pantomime and to imitation. Gestural performance was quantified as accuracy on five performance dimensions; a composite score, an arithmetic combination of the five performance dimensions, was used as an index of the overall accuracy. Analyses revealed a comparable proportion of patients in each stroke group were classified as apraxic in the imitation condition, but a higher proportion of left stroke patients were apraxic in the pantomime condition. The severity of apraxia in each stroke group and the performance dimensions affected were, however, comparable. Analyses of the patterns of apraxia (pantomime alone, imitation alone or apraxia in both conditions) revealed a higher frequency of apraxia in both stroke groups for the pattern reflecting apraxia in both conditions, indicating that a disruption at the movement execution stage of gesture performance was most common.     

Childhood Gender Nonconformity and Body Dissatisfaction in Gay and Heterosexual Men

Although researchers have long hypothesized a relation between gender role orientation (i.e., masculinity and femininity) and body dissatisfaction, findings have been inconsistent. The current study employed a measure of recalled childhood gender nonconformity to examine gender role behaviors in association with body dissatisfaction among an ethnically diverse (76% Caucasian, 2% African American, 8% Asian, and 16.4% Hispanic American) group of predominantly college-aged males of both homosexual (n = 129) and heterosexual (n = 52) orientation. Consistent with past research, gay males reported more body dissatisfaction and recalled more childhood gender atypical behaviors (e.g., disliking athletics, playing with dolls). Group differences in body dissatisfaction, however, disappeared when childhood gender nonconformity was statistically controlled, suggesting childhood atypical gender role behavior may place males at greater risk for adult body dissatisfaction. A within-group analysis also found that a high feminine subtype of gay males had greater body dissatisfaction than less feminine subtypes had. Results support the assertion that gender role behaviors may contribute to body dissatisfaction among gay males.     

Low-frequency acoustic modulations generated by the high-frequency portion of the cochlea, noninvasively recorded from the scalp of mice (Mus musculus)

Vocalizations often contain low-frequency modulations of the envelope of a high-frequency sound. The high-frequency portion of the cochlear nerve of mice (Mus musculus) generates a robust phase-locked response to these low-frequency modulations, and it can be easily recorded from the surface of the scalp. The cochlea is most sensitive to envelope modulation frequencies of approximately 500 to 2000 Hz. These responses have detection thresholds that are approximately 10 dB more sensitive than auditory brainstem responses, and they are very sharply tuned. These measurements may provide a nontraumatic means of repeatedly assessing cochlear functions involved in sound localization and perception of vocalizations.     

Numerical competence in rats (Rattus norvegicus): Davis and Bradford (1986) extended

The task of rats (Rattus norvegicus) was to enter 1 box of a defined ordinal number among an array of boxes. In Experiments 1 and 2, the rats correctly chose the 4th box from arrays of 6 and 12 boxes, respectively. In Experiments 3 and 4, in which the ordinal number of the correct box was increased in a graduated fashion, they were able to select the correct box even when its position was higher than 10th among 12 and 18 boxes, respectively. In Experiment 5, the possibility that the rats had used cues to the openability of the box doors was ruled out. In Experiments 6 and 7, the rats succeeded in the task even when the total number of boxes was varied from trial to trial. In Experiment 8, both small- and large-sized boxes were used to control for the possibility of using the cumulative length of the boxes as a cue. Overall, the results suggest that performance was based on numerical cues. Intentional acts were occasionally observed but appeared not to be essential for solving the task.