Amorphized cellulose as filler in biocomposites based on poly(ɛ-caprolactone).

Amorphous cellulose particles, obtained through a solvent-free mechano-chemical process, have been tested for the first time as a potential filler for biodegradable composites based on poly(ɛ-caprolactone) (PCL). Commercial cellulose fibers have been also tested for comparison. An effective interfacial strategy based on a compatibilizing agent, a modified PCL, has been used to improve the polymer/filler interfacial adhesion. Composites have been tested through physico-mechanical characterizations and soil burial degradation tests, in order to evaluate the influence of cellulose structure and morphology and polymer/filler interfacial adhesion on the final properties of the realized materials. The use of the amorphous cellulose particles combined with the presence of a suitable interfacial agent has allowed to modulate relevant technological properties of the realized composites, such as tensile and thermal properties, water absorption, water vapor transmission rate and biodegradation kinetic.

Eye movement patterns in linguistic and non-linguistic tasks in developmental surface dyslexia.

Ten subjects who could be reliably assessed as surface dyslexics were selected on the basis of a large test battery. Eye movements in non-linguistic and linguistic tasks were studied in these subjects. Stability of fixation on a stationary stimulus was examined. Performance of dyslexics was no different from that of an age-matched control group. Similarly, no difference was observed between the two groups when they were requested to saccade to a rightward or leftward target. On the other hand, while reading short passages, dyslexics showed an altered pattern of eye movements with more frequent and smaller rightward saccades as well as longer fixation times. The reading pattern was analysed by eye tracking. Numerous fixations were used to read a single word in a fragmented way. Longer words showed a higher number of fixations. Overall, it was concluded that surface dyslexia is not associated with oculo-motor dysfunction and the study of eye movements in reading reveals the processing through orthography-to-phonology conversion characteristic of surface dyslexia. The importance is stressed of examining selected groups of subjects in the psychophysiological study of dyslexia.

Effects of parietal lesions in humans on color and location priming.

To determine whether the parietal lobes contribute tot he selection of nonspatial features known to be processed in the ventral stream, the current study examined the effect of chronic unilateral parietal lobe lesions in humans on color and location priming. Patients and normal controls performed a go/no-go color discrimination task in which either the same color and different color pairs of stimuli (prime and probe) were projected sequentially either in the same hemifield or in opposite hemifields. Control subjects and patients both showed independent effects of color and location priming. In the patients, primes in either field produced color priming for target probes in the ipsilesional field but not for probes in the contralesional field. This observation implicates the parietal cortex in processing activated codes of stimulus attributes not only for spatial information but also for visual features processed in the ventral visual pathways.

Let not thy left hand know what thy right hand knoweth. The case of a patient with an infarct involving the callosal pathways.

Following a cerebral vascular accident, a patient showed a classical disconnection syndrome: left-hand tactile anomia, apraxia and dysgraphia and right-hand constructional apraxia. What made the case unusual was the presence of hand asymmetry in the performance of some matching-to-sample tasks carried out in foveal vision. The left hand committed significantly more errors than the right hand when it was not possible to identify on a perceptual basis the stimulus that was to be matched, because it was removed (memory condition) or was indicated verbally (verbo-visual matching), or had the same name but not the same physical appearance as the match (capital and lower-case letter matching). No hand difference emerged when the stimulus remained in full view throughout the matching task (perceptual condition). The hand effect, however, was limited to colours and letters. Objects, geometrical shapes and unfamiliar faces were matched with equal proficiency by both hands under every condition of presentation. Left-hand errors also significantly outnumbered right-hand errors in sorting colours according to hue and colouring drawings. MRI showed an infarct in the left cingulate white matter that ran parallel to the trunk of the corpus callosum, and an infarct of the splenium. However, the latter did not prevent the transmission of colour and letter information between the two hemispheres, as shown by the performance on perceptual equivalence tasks and by the correct right-hand responses to stimuli projected to the left visual field. We propose that this pattern of deficit is contingent upon the specific role that the left hemisphere plays in categorizing a given colour patch as belonging to a definite colour region (red, blue, etc.) and in grapheme recognition. Without the assistance of the left side the right hemisphere lacks the benefit provided by meaning identification. In our patient the left brain did receive information from the right brain and was able to process it, but was prevented by the paracallosal lesion from transmitting what it knew to the right motor area. No hand effect emerged for objects and geometrical shapes, because their semantic memory is bilaterally represented.

Developmental surface dyslexia is not associated with deficits in the transient visual system.

Deficits of the transient visual system have been reported in unselected groups of dyslexics. The aim of this study was to examine whether this finding holds when subjects with a specific type of developmental reading disorder (surface dyslexia) are considered. Ten Italian children were examined. They all presented the characteristic markers of surface dyslexia: slow and laborious reading with errors in tasks which cannot be solved with a grapheme-phoneme conversion (i.e., homophones). Contrast sensitivity thresholds to phase-reversal gratings were within normal limits for most subjects both for stimuli presented centrally and in the right parafovea. This indicates that developmental surface dyslexia is not associated with a deficit in the transient system. In contrast, sensitivity to high spatial frequency stationary stimuli was reduced.

Response bias in color priming.

Four experiments investigated the role of response bias in color priming. Subjects were shown three prime-target pair conditions: same color trials, category priming trials (in which prime and target were different colors associated with the same response category) and incongruent trials. The subjects' task ('go-no-go' vs. 'two-choice' RT, Experiments 1-2), the categorization criterion of the stimuli (Experiment 3) and the proportion of the same versus different response trials (Experiment 4) were manipulated to influence the amount of response bias. Overall, the results indicate that color priming is produced whether or not a bias is generated at the response level, suggesting that the mechanisms underlying the two effects are largely independent of each other.

Selective reading slowness in a traumatic patient with impairment in basic visual processes.

Following a closed-head injury, G.M., a 17-year-old male, showed a reading disturbance in the absence of other cognitive deficits. G.M.'s reading was exceedingly slow, although virtually error free. Analysis of his disorder indicated an inability to read words presented tachistoscopically to the left (spared) visual field. Therefore the reading deficit cannot be interpreted as simply due to the visual field reduction (hemianopic alexia). Reading speed was clearly affected by word length, a finding typical of letter-by-letter reading. Both behavioral and psychophysical testing indicated a selective reduction of visual discrimination and detection (particularly in the range of high spatial frequency information) in portions of the left hemifield which appeared spared upon perimetric examination. Overall, it is suggested that the reading deficit, phenomenologically similar to that of other letter-by-letter readers, can be interpreted as due to a combination of basic visual perturbations: visual field cut with macular splitting and deficit of processing of high spatial frequency information.

Priming effect in a color discrimination task.

Two experiments were run to test whether the automatic coding of colors generates priming effects. Subjects were tachistoscopically presented a series of prime-target sequences. The prime stimulus could be either a red, green, or black circular dot, followed by a red or green annular ring (target). The role of automatic and conscious mechanisms was investigated in Exp. 1 by manipulating the predictive validity of the prime stimuli (80%, 50%, 20%), keeping constant the value of stimulus-onset asynchrony (350 msec.). Analysis showed priming effects even in the low predictive condition, where no conscious expectations could be activated. In Exp. 2, three different values of stimulus-onset asynchrony were used, 150, 350, and 2100 msec. Priming effects were obtained in the short and medium stimulus-onset asynchrony condition but not in the long one. Over-all, the data of both experiments produce converging evidence which indicates that the automatic elaboration of colored stimuli may produce priming effects.

Semantic processing of unattended parafoveal words.

The influence that a context word presented either foveally or parafoveally, may exert on the processing of a subsequent target word was studied in a semantic decision task. Fourteen subjects participated in the experiment. They were presented with word-nonword pairs (prime). One member of the pair (which the subjects had to attend to) appeared centrally, the other parafoveally. The prime was followed by a target at two inter-stimulus intervals (ISI; 200 and 2000 msec). The word stimulus of the pair could be semantically related or unrelated to the target. The subjects' task was to classify the target as animal or not animal by pressing one of two buttons as quickly as possible. When the target word was semantically associated with the foveal (attended) word the reaction times were faster for both ISIs; when it was associated with the parafoveal (unattended) word in the prime pair, there were facilitatory effects only in the short ISI condition. A second experiment was run in order to evaluate the possibility that the obtained results were due to identification of the parafoveal stimulus. The same prime-target pairs of experiment 1 (without the target stimuli) were used. The prime-target pairs were presented to fourteen subjects who were requested to name the foveal (attended) stimulus and subsequently, if possible, the parafoveal (unattended) one. Even in this condition, percentage of identification of the unattended word was only 15%, suggesting that previous findings were not due to identification of unattended stimuli. Results are discussed in relation to Posner and Snyder's (1975) dual coding theory.