ABSTRACT
Representations involved in two construction-related tasks were analyzed by multidimensional scaling (MDS), a statistical technique that allows the dimensions of internal representations to be derived from empirically obtained judgment data. The tasks involved judgments of how similar two objects were and how well they fitted together; these judgments are related to copying and assembly abilities that are impaired in constructional apraxia. Analyses of numerical subjective ratings and response times for these judgments showed that within the same set of geometric objects, different shape-related properties were emphasized under different task conditions. The similarity judgment depended most on a representational dimension related to enclosure of space, while the fit judgment depended to a greater extent on a dimension related to the objects' symmetry properties. This pattern of results was found in both subjective ratings and response times, as analyzed by MDS and by confirmatory classical statistics. The findings suggest that construction-related tasks depend on representations that are context-dependent, and that MDS may be useful in a variety of settings as an intermediate-level tool for analyzing representations related to context-specific abilities.
Subject(s)
Pattern Recognition, Visual/physiology , Psychomotor Performance/physiology , Adult , Apraxias/physiopathology , Female , Humans , Male , Movement/physiology , Multivariate Analysis , Photic Stimulation , Space Perception/physiologyABSTRACT
This study analyzed neuronal responses in the second somatosensory (SII) and 7b cortical areas during a selective attention task. Cues directed attention to one of three simultaneous stimuli: vibrotactile stimuli applied to mirror sites on both hands or to a similarly timed auditory tone. Two stimulus patterns appeared with equal probability for the cued stimulus: a constant amplitude sinewave or the latter with a superimposed brief amplitude pulse midway in the trial. Uncued stimuli always contained amplitude pulses. Monkeys demonstrated whether an amplitude pulse at the cued location was present or absent by making appropriately rewarded up and down foot pedal movements. Cue location and stimulus pattern varied trial-wise and pseudo-randomly. Average firing rates to vibrotactile stimuli in 82 of 181 SII cells and 13 of 22 area 7b cells differed significantly during at least one epoch for trials cued to the contralateral hand when compared to trials cued to the ipsilateral hand or auditory stimulus. Predominant were relatively suppressed firing rates during times prior to the epoch containing the amplitude pulses or enhanced activity during and after these pulses. Generally, different cells showed suppression early vs enhancement later in a trial. Analyses of the ratio between firing rates before and during the amplitude pulses suggested improved evoked signals to the amplitude pulses. The discussion considers attention as a mechanism for reducing distractions, early in the trial through suppressing these signals, or for selectively increasing response magnitudes in the cued channel, especially around times when amplitude pulses were present or absent.
Subject(s)
Attention/physiology , Cerebral Cortex/physiology , Somatosensory Cortex/physiology , Spatial Behavior , Touch/physiology , Acoustic Stimulation , Analysis of Variance , Animals , Cerebral Cortex/cytology , Cues , Functional Laterality/physiology , Macaca mulatta , Male , Neurons/physiology , Somatosensory Cortex/cytology , Stress, MechanicalABSTRACT
Selective spatial attention has a greater effect on detection of the absence of an amplitude change than it has on detection of the presence of such a change. Attention to one of four fingertips was manipulated by an 80% valid tactile cue in two-interval forced-choice tasks. In one task, the target was a vibrotactile amplitude change appearing among constant-amplitude distractors; in the other task, targets of constant amplitude had to be detected amid amplitude changes at the other fingertips. Cuing had a greater effect on the latter task than it did on the former. This asymmetry is consistent with the presence-absence asymmetry found in visual search and does not depend on the difficulty of the two tasks. A statistical model shows that a pooled activity mechanism could account for these experimental results.
Subject(s)
Attention , Touch , Vibration , Adult , Female , Functional Laterality , Humans , Male , Psychomotor Performance , Reaction Time , Sensory ThresholdsABSTRACT
Hyperpigmentation of the hands and feet developed in a 65-year-old Korean woman who had undergone a total gastrectomy and esophagojejunostomy due to early gastric cancer 7 years previously. A diagnosis of megaloblastic anemia due to vitamin B12 deficiency was made. In the areas of pigmentation, there were abnormally large nuclei in the keratinocytes. All of these findings were reversible upon the administration of vitamin B12. Ultrastructurally, there were many intracytoplasmic desmosomes, numerous aggregated bundles of tonofilaments, and highly condensed keratohyalin granules. The pathophysiologic mechanism of vitamin B12 deficiency associated with pigmentary disturbances and change of nuclear size is discussed.
Subject(s)
Anemia, Macrocytic/etiology , Anemia, Megaloblastic/etiology , Pigmentation Disorders/etiology , Vitamin B Deficiency/complications , Anemia, Megaloblastic/diagnosis , Anemia, Megaloblastic/drug therapy , Biopsy , Cobamides/therapeutic use , Female , Gastrectomy/adverse effects , Hand Dermatoses/pathology , Humans , Middle Aged , Skin/pathology , Vitamin B Deficiency/drug therapy , Vitamin B Deficiency/etiologyABSTRACT
A case of squamous cell carcinoma (SCC) arising in a lesion of Hailey-Hailey disease at the penoscrotal junction is reported. The patient was treated with arsphenamine (Salvarsan 606) early in the disease. It is possible that this carcinogen, as well as friction and the local irritation of long-standing Hailey-Hailey skin lesions, may be the predisposing factors for the development of SCC in this case.
