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Spatial representations of words and nonwords.

The first two experiments investigated whether the representations of words, besides being unitary, are also spatial in nature. Subjects were required to search for target letters in either five-letter words or five-letter nonwords. They were instructed to press the right-side key for one target and the left-side key for the other target. The center item of the letter string was always at fixation. Targets appeared one at a time, located at the second (left side) or the fourth (right side) position within the letter string. The results showed that: a) responses to targets within words were faster than responses to targets within nonwords (the word-superiority effect); b) responses to compatible stimulus-response pairings were faster than responses to incompatible stimulus-response pairings (the spatial compatibility, or, more precisely, the Simon effect); and c) in Experiment 2, left-side targets were responded to faster than right-side targets within nonwords (the left-right scanning effect). It was concluded that representations of both words and nonwords are spatial in nature. Experiment 3 was aimed at testing whether the spatial layout of the representations of words is always along the left-right horizontal dimension, regardless of the topographic transformation of the stimulus. The same words and nonwords used in the previous experiments were shown vertically and the subjects were required to make left-right discriminative responses to upper and lower target letters. The results showed the word-superiority effect but no spatial compatibility effects. It was concluded that the representation of a vertically presented word is vertically arranged.

Adult↗

Spatial compatibility effects on the same side of the body midline.

Stimulus-response compatibility effects have been hypothesized to result (a) from a subject's innate tendency to respond in the direction of the source of stimulation, (b) from a correspondence between the spatial codes associated with the effector and the stimulus, or (c) from an attentional bias favoring the effector located in the same hemispace as the command signal. Two experiments were conducted to test these three hypotheses. In Experiment 1 the subjects were requested to make unimanual discriminative key-pressing responses to two light stimuli, both appearing to either the right or left of the fixation point. In one condition the two hands were in anatomical position (uncrossed); in the other they were crossed. The procedure of Experiment 2 was similar to that of Experiment 1 with the exception that both hands, always in an uncrossed position, were placed on the same side of the body midline (on the right or left). The results showed that the compatibility effect depends on a correspondence between the spatial codes associated with the location of the effector and the location of the command stimulus.

Adult↗

Spatial S-R compatibility with orthogonal stimulus-response relationship.

Spatial stimulus-response (S-R) compatibility with unimanual two-finger choice reactions was investigated under conditions in which the spatial orientation of response keys was either parallel to or perpendicular to the orientation of the stimuli. Subjects responded to green or red lights in the left or right visual field (irrelevant stimulus location). The response keys were oriented horizontally on the left or right side of the body midline parallel to the stimuli, and were pressed with the palms facing down (Condition A), or were oriented orthogonally to the stimuli in the midsaggital plane, either horizontally and pressed with palms facing down (B) or facing up (C), or vertically and pressed with palms facing the body (D). The results for Condition A demonstrate the usual spatial S-R compatibility effect between field of stimulation and spatial position of responding finger. For Conditions B and D, a strong reaction time advantage still obtained for those stimulus-finger pairings that are compatible under Condition A. Condition C revealed an RT advantage for the opposite pairings. This shift of the compatibility effect from Condition B to Condition C indicates that the left/right distinction of fingers does not follow a simple, fixed spatio-anatomical mapping rule. The results are discussed within the framework of a hierarchical model of spatial S-R compatibility, with spatial coding and spatio-anatomical mapping as factors.

Adult↗

Laterality of cross-modal spatial processing.

This study examined the laterality of spatial-form perception in normal adults using a cross-modal matching paradigm involving visual and tactile processing. Randomly generated eight-point and 12-point Vanderplas and Garvin (1959) patterns were used as the stimuli. In a visual-to-tactile task, a lateralized visual pattern was followed immediately by a haptic task requiring subjects to discriminate which of two simultaneously felt shapes matched the visual pattern. In a tactile-to-visual task, subjects decided which of two simultaneously felt shapes matched a lateralized visual pattern presented after haptic manipulation. There were no main effects for laterality or for sex differences. Matching accuracy was better in the visual-to-tactile task and for less complex stimuli. A visual field by feeling hand interaction showed best recognition accuracy when visual-feeling hand combinations on the same side of the body were used in the two matching tasks. These data reflect a stimulus-response compatibility explanation of spatial-form perception that is consistent with a behavioral and not a cerebral asymmetry model.

Adult↗

Are movements prepared in parts? Not under compatible (naturalized) conditions.

This set of experiments is concerned with the specification of movement parameters hypothesized to be involved in the initiation of movement. Experiment 1 incorporated the precuing method developed by Rosenbaum in which a precue provided partial information of the upcoming movement before the stimulus to move. Under conditions in which precues were provided by letter symbols and stimuli were color-coded dots mapped to response keys. Rosenbaum found reaction times to be slower for the specification of arm than for direction, and both to be slower than the specification of extent. In Experiment 1, using precue and stimulus conditions that paralleled those employed by Rosenbaum, we obtained very similar findings. The three follow-up experiments extended these findings to more naturalized stimulus-response compatible conditions. We used a method in which precues and stimuli were directly specified through vision and mapped in a one-to-one manner with responses. In Experiment 2, although reacion times decreased as a function of the number of parameters precued, there were no systematic effects of precuing particular parameters. In Experiments 3 and 4, we incorported an ambiguous precue that, while serving to reduce task uncertainty, failed to provide any specific information as to the arm, direction, or extent of the upcoming movement. Initiation times did not systematically vary as a function of the type of parameter precued nor were there significant differences between specific and ambiguous precue conditions. In sum, only in Experiment 1 in which precues and stimuli involved complex cognitive transformations was there support for Rosenbaum's parameter specification model. When we employed highly compatible conditions, designed to reflect a real-world environment, we failed to obtain any tendency for movement parameters to be serially specified. We discuss grounds for suspecting the generality of parameter specification models and propose an alternative approach that is consonant with the dynamic characteristics of the motor control system.

Adolescent↗

Effects of severe closed-head injury on three stages of information processing.

The present study investigated the loci of the information-processing delay that characteristically follows severe closed-head injury (CHI). Sternberg's additive-factors logic was used to determine the effects of severe CHI on the central information-processing stages of stimulus encoding, memory comparison, and decision-making/response-selection. The task variables used to define the stages operationally were stimulus quality, memory set size, and stimulus-response compatibility. Twenty subjects who had sustained a severe CHI more than 18 months earlier and 20 matched control subjects completed a stimulus encoding by response selection task in Experiment 1, and a Sternberg high-speed memory scanning task in Experiment 2. The CHI group performed the stimulus encoding and decision-making/response-selection stages of processing significantly slower than did the control group. However, no significant group differences were found on the memory comparison stage, suggesting that memory comparison processes may be relatively intact in long-term patients with severe head trauma. The results are discussed in relation to a global and a late-specificity hypothesis of central processing deficits following severe CHI. The possibility that cognitive processes demanding less attention may be more resilient to injury is also considered.

Adult↗

Influence of anatomical factors and spatial compatibility on the stimulus-response relationship in the absence of the corpus callosum.

Simple and choice reaction times (RTs) to lateralized flashes of light were measured in two acallosal subjects, a callosotomized patient with sparing of the splenium, six IQ-matched controls and six controls with above average IQ. The aim of the study was to investigate the influence of stimulus-response factors on visuomotor integration in the absence of the corpus callosum. The results showed that simple-RTs are faster for all groups when sensory input and motor output are coordinated in the same hemisphere, regardless of the spatial relationship between stimulus (S) and response (R). The difference between ipsilateral and contralateral RTs, taken as a measure of interhemispheric transmission time (ITT), was more than three times longer in the patients lacking the corpus callosum than in the controls. In the choice-RT paradigm, the main determinant of the response speed was S-R spatial compatibility rather than the anatomical relationship between the neural structures receiving the visual input and those controlling the motor output. Spatially compatible S-R pairings were always faster than incompatible pairings. The compatibility effect was present in all subjects but it was significantly larger in the callosum-deprived patients and their IQ-matched controls with respect to the high-IQ controls. The latter finding suggests that cognitive factors may be involved in the production of the spatial compatibility effect.

Adult↗

Inhibition by verapamil of neutrophil responses to formylmethionylleucylphenylalanine and phorbol myristate acetate. Mechanisms involving Ca2+ changes, cyclic AMP and protein kinase C.

Verapamil inhibits in human neutrophils the respiratory burst, the secretion and the change of transmembrane potential induced by formylmethionylleucylphenylalanine, a Ca2+-dependent stimulus, and by phorbol myristate acetate, a Ca2+-independent stimulus. Besides the blocking of Ca2+ channels, many mechanisms are responsible for the inhibition of neutrophil responses. In fact, verapamil (i) increases the intracellular cAMP concentration, potentiates the cAMP response induced by the chemotactic peptide and induces the appearance of a cAMP response also when the stimulant is phorbol myristate acetate; (ii) causes a decrease of Ca2+ association to cell membranes, so depleting the pools of exchangeable Ca2+ and depressing the 'Ca2+ response' in terms of rise in [Ca2+]i monitored with Quin 2 and of rapid mobilization from cell membranes monitored by chlorotetracycline fluorescence change; (iii) inhibits the Ca2+-activated phospholipid-dependent protein kinase C. The data, discussed in relation to the biochemical mechanisms of the stimulus-response coupling, are compatible with the hypothesis of an involvement of the activation of protein kinase C as key step in the sequence of transduction events for the induction of many neutrophil functions.

Calcium↗

Serial reaction time as a function of the nature of repeated events.

Past research into the phenomenon of reduced latency to repeated events in serial reaction time tasks resulted in attempts to partition reaction time into components attributable to separate cognitive processes. These attempts focused on many-to-one condensing paradigms, which permitted direct assessment of the effect of response-only repetitions but not stimulus-only repetitions. The three experiments reported in the present study used a technique designed to overcome this limitation. It was found that repetition of only the symbolic content of the total stimulus-response event was a sufficient condition for a reduced response latency and that response-only repetitions tended to be facilitative only when stimulus-response relations were compatible. These and related findings were discussed with respect to their bearing on contemporary issues concerning the analysis of cognitive operations into separable and additive components.

Discrimination, Psychological↗

Latencies of event related potentials as a tool for studying motor processing organization.

The aim of this experiment was to better define the relative organization of motor processing using both behavioral measures and ERPs. Using the additive factors method, three motor variables; (1) stimulus-response (S-R) compatibility, (2) movement extent, and (3) time uncertainty, were all manipulated in a visuo-bimanual, four-choice, pointing task. As expected, all three variables significantly lengthened RT without interaction. All three motor variables also affected ERP latencies. Both P300 and N200 latencies were lengthened by greater movement extent. Moreover, N200 and P300 latencies were differentially affected by S-R compatibility and time uncertainty. Finally, both RT-minus-N200 and RT-minus-P300 were significantly lengthened by S-R incompatibility and greater time uncertainty whereas movement extent had no effect. In sum, ERP results did not support the assumptions of the classical serial model but rather of a contingent-parallel model. Furthermore, the ERP data can be used to infer the relative order of the different stages in this model.

Adult↗

Effects of S-R mapping and response modality on performance in a Stroop Task.

Forty subjects performed a choice reaction time task in which the stimulus was the word Red or Green printed in either red or green ink. Subjects responded verbally in one block of trials and by key pressing in another block. For one group, ink color was the relevant cue, and for another group, the word was the relevant cue. Half of the subjects in each group were instructed to make the response that corresponded to the relevant cue (compatible S-R [stimulus-response] mapping); the other half were instructed to make the response that did not correspond (incompatible S-R mapping). In general, subjects who performed under compatible S-R mapping instructions reacted faster when the irrelevant cue corresponded to the response than when it did not. In contrast, subjects show performed under incompatible S-R mapping instructions reacted faster when there was a lack of correspondence between the irrelevant cue and the response than when there was correspondence. Results were consistent with a notion of logical recoding; that is, that instructing subjects to recode the relevant cue into the alternate color may have caused them to recode the irrelevant cue in the same logical manner. Results might also be interpreted to suggest that the Stroop effect is related to congruence between the relevant and the irrelevant cues rather than to correspondence between the irrelevant cue and the response.

Color Perception↗

The effects of videogame playing on the response selection processing of elderly adults.

Within an information processing framework, age-related declines in speeded responding are attributed to one or more stages of processing. It was the purpose of this experiment to demonstrate the potential reversibility of this decline in at least one processing stage, response selection. Two groups of elderly participants (57 to 83 years) were pretested on a two-choice reaction time (RT) task under two levels of spatial stimulus-response (S-R) compatibility, a task demand shown to affect response selection. Following the pretest, one group participated in 7 weeks of videogame play, whereas a second group did not. All participants were posttested on the same two-choice RT task. The results of the analysis of covariance revealed that those elderly individuals who played videogames were faster than the control participants under both levels of S-R compatibility. The effect of videogame play, however, was greater for low compatibility. These results are taken as support for a potential to improve response selection through videogame play.

Aged↗

Androgyne becomes bisexual in sexological theory: Plato to Freud and neuroscience.

Plato conceptualized primordial humans as androgynes, the children of the moon. The primordial hermaphroditism of the mammalian embryo became known 2 1/2 millennia later in the mid-19th century. By 1864 Ulrichs had transposed the new knowledge from embryology to sexology to explain those to whom he gave the name Urnings (after Uranus who gave womanless birth to Venus from sea spume) as having "a woman's mind trapped in a man's body" (anima muliebris corpore virili inclusa). Urning became displaced by sexual inversion, and eventually by homosexual, a term coined together with heterosexual by Kertbeny as recently as 1869. The embryological principle of primordial hermaphroditism became linked to evolutionary Darwinism by way of Haeckel's principle of recapitulation, epitomized as "ontogeny recapitulates phylogeny." The recapitulation principle became linked, in turn, to the principle of intrapsychic primordial bisexuality, which became a cornerstone of Freud's psychoanalytic theory. Genetics influences the outcome of bipotentiality not directly but by way of hormonal programming of the brain, prenatally or neonatally, rather than pubertally and in maturity. Bipotentiality within the brain has been investigated chiefly in the hypothalamus where male/female dimorphism has been recognized, but its determinants and stages of differentiation, both prenatal and postnatal, remain to be fully ascertained. Neuroanatomical research on the outcome of male/female bipotentiality as gay, straight, or in between is politically and morally opposed by those who postulate a bipotential preference or voluntary choice. In stimulus-response associationism, to which behavior-modification theory belongs, bisexuality is equipotential, and either alternative may be evoked, ostensibly, dependent on the stimulus situation. In ethological theory, the effectiveness of stimulus-response bonding is confined chronologically to a critical period of development and is restricted phylogenetically by an innate recognition mechanism and an innate releasing mechanism. These limits are compatible, however, with some degree of both individual and ethnic variation.

Bisexuality↗

Transmembrane calcium movements mediated by ionomycin and phosphatidate in liposomes with Fura 2 entrapped.

A novel liposomal method permits studies of Ca movements across the bilayers of multilamellar vesicles (MLV) which had entrapped the Ca-dependent, fluorescent indicator dye Fura 2. Ionomycin-mediated Ca translocation across MLV of phosphatidylcholine (PC)/dicetyl phosphate (DCP), 9:1, obeyed simple first-order kinetics since log-log plots of initial rates versus ionomycin or Ca concentration yielded slopes of approximately 1. Since Ca is translocated in a Ca-dependent fashion in the course of stimulus-response coupling of cells which form diacylglycerol (DAG) and phosphatidate (PA) from polyphosphoinositides, we compared effects of PA with those of DAG. PA and DAG were preincorporated in PC/DCP vesicles, in which trace amounts of ionomycin provided transmembrane potential (due to Ca2+/H+ exchange). Significant increases in Ca movements were observed in the presence of egg lecithin PA, dioleoyl-PA, and dipalmitoyl-PA when compared with DCP- or DAG-containing MLV. DAGs such as 1-oleoyl-2-acetoylglycerol or 1,2-dioleoylglycerol in liposomes decreased rates of Ca translocation. Ca influx into PA-containing MLV was dependent on the mole percent of the PA in bilayers; the complex kinetics of Ca influx were compatible with the formation of nonbilayer states. Incorporation of cholesterol into the liposomes inhibited initial rates of Ca uptake by MLV presumably by condensing the bilayers. Ca influx increased with increasing pH of the external medium from 6.9 to 7.9 in liposomes with an internal pH of 7.4.(ABSTRACT TRUNCATED AT 250 WORDS)

Benzofurans↗

Evaluation of compatibility effects in the precuing of arm and direction parameters.

The present study evaluated the role of compatibility effects in the precuing of arm and direction parameters. In the first two experiments different stimulus and response arrangements were examined. For all three experiments the spatial precue and imperative stimuli were compatibly assigned to responses (i.e., a direct correspondence existed between the stimulus and response locations). Experiments 1 and 2 indirectly tested the effect of decision processes required by the stimulus-response set. Experiment 1 replicated previous research that has found longer reaction times for the direction uncertain parameter as compared to arm uncertain. Experiment 2 examined the precuing of arm and direction parameters with stimuli that maintained right-left arrangements for both parameters. Unlike Experiment 1, reaction times did not differ for precuing the two movement parameters. Experiment 3 directly examined the effect of differential decision requirements from up-down spatial stimuli and right-left spatial stimuli for a single parameter. In support of results from the first two experiments, results indicated longer reaction times for decisions from up-down stimuli as compared to right-left stimuli. Because reaction times for precued movement parameters are a function of the stimulus and response arrangements used, differences in reaction times are most likely due to compatibility effects arising from differences in the spatial arrangements of the precued stimulus and response set.

Arm↗

The effects of lower body negative pressure on baroreceptor responses in humans.

In healthy human subjects the immediate responses of pulse interval and the steady-state responses of arterial blood pressure and cardiac output to changes in carotid sinus transmural pressure were determined before and during the application of a subatmospheric pressure to the lower part of the body. Increases in carotid sinus transmural pressure, effected by applications of subatmospheric pressure to the neck (neck suction) resulted in prolongation of pulse interval and decrease in blood pressure; opposite responses were obtained to application of a positive pressure (neck pressure). Application of lower body negative pressure resulted in a decrease in pulse interval (heart rate increase) but little change in blood pressure. During lower body negative pressure, the responses of pulse interval to neck pressure were reduced but those to neck suction were unaffected; the responses of blood pressure to neck suction were enhanced but those to neck pressure were unaffected. From experiments in which cardiac output was also determined, it was seen that lower body negative pressure reduced cardiac output, increased calculated total body vascular resistance and augmented the resistance response to neck suction although not to neck pressure. These results are compatible with the view that application of lower body negative pressure does not change the sensitivity of the baroreceptor reflex and that the changes in the responses are due to non-linearities of the stimulus-response curves.

Adult↗

Coding of information about tactile stimuli by neurones of the cuneate nucleus.

1. The responses of cuneate neurones to controlled tactile stimulation of the foot pads were examined in unanaesthetized, decerebrate cats. The neurones were divided into three functional classes; one sensitive to steady tactile stimuli, and two dynamically sensitive classes which could be readily differentiated by their responsiveness to cutaneous vibration. Each class appeared to receive an exclusive input from only one of the three known groups of tactile receptors associated with the foot pads, namely the Pacinian corpuscles, the Merkel endings and the intradermal, encapsulated endings known as Krause or Meissner corpuscles. 2. Cuneate neurones responsive to steady indentation of the skin displayed approximately linear or sigmoidal stimulus-response relations over indentation ranges up to approximately 1.5--2 mm. Response variability at a fixed stimulus intensity was relatively low and showed little systematic change over the full range of the stimulus-response curves. 3. One class of dynamically sensitive cuneate neurones responded to cutaneous vibration over a range of approximately 5-80 Hz with maximal responsiveness around 30 Hz. The other class, the Pacinian neurones, responded over a range of approximately 80- greater than 600 Hz with maximal responsiveness at 200-400 Hz. The thresholds and combined band width of vibratory sensitivity of these populations were comparable with known subjective thresholds and range of cutaneous vibratory sensibility. 4. Responses of cuneate neurones were phase-locked to the vibratory stimulus suggesting that information about vibration frequency could be coded by the patterns of impulse activity. Quantitative measures indicated that maximal phase-locking occurred in responses to vibration frequencies of 10-50 Hz with a progressive decline at higher frequencies. Above 400 Hz, impulse activity occurred almost randomly throughout the vibratory stimulus cycle and therefore carried little further signal of vibratory frequency. The decline, with increasing frequency, in the ability of cuneate neurones to signal information about vibratory frequency parallels the known subjective capacities for frequency discrimination. 5. A switch-over occurred at approximately 80 Hz in the population of cuneate neurones able to provide the more reliable signal of vibratory frequency; above 80 Hz, the Pacinian neurones; below 80 Hz, the neurones receiving intradermal, rapidly adapting receptor input from the pads. 6. The observed properties of cuneate neurones are compatible with a role in signalling information which could contribute to subjective tactile abilities.

Action Potentials↗