Giant cutaneous horn: a patient report

A large cutaneous horn was excised from the left side of the nose and cheek of a 68-year-old woman. Reconstruction was performed with a split-thickness skin graft. Histologically the lesion represented squamous cell carcinoma. The nature of malignant degeneration in cutaneous horns is discussed.     

Dorsal horn cells that respond to stimulation of distant dorsal roots

Experiments were carried out to find if there were post-synaptic effects produced by impulses in the long ranging primary afferents, which had been shown by Wall & Werman (1976) to extend from upper lumbar dorsal roots to the sacral segments. Dorsal rootlets were stimulated in decerebrate low-spinal adult cats.1. The dorsal root potential and ventral root reflex were recorded on S1 root filaments, in response to stimulation of dorsal rootlets extending from L1 to S1. With increasing distance between stimulating and recording segments, these potentials became smaller and more delayed. In two animals, there was no response at S1 to stimulation of L1 and L2 dorsal roots.2. In all animals, stimulation of L3 or L4 dorsal roots produced cell responses in dorsal horn segments L7 or S1. The density of such cells was variable, from animal to animal. Responding cells were mainly concentrated laterally in the dorsal horn.3. The latency and response variability of L7-S1, dorsal horn cells to L3-L4 stimulation was consistent with at least some of them being fired monosynaptically.4. Cells that respond to stimulation of one distant rootlet respond to many closer rootlets as well.5. The receptive fields of L7-S1 dorsal horn cells, responsive to stimulation of L3-L4 rootlets, were typical of those generally found in the L7-S1 segments, and were at some distance from the L4 dermatome. Only twenty cells had receptive fields which extended into the dermatome of the rootlets stimulated.6. It was established that some L4 cells respond to S1 dorsal root stimulation, just as the main study had shown that S1 responds to L4.7. It is concluded that substantial numbers of dorsal horn cells, including cells with many types of cutaneous receptive field, respond to two classes of synaptic in-put: one effective in firing the cell upon natural cutaneous stimulation, and one relatively ineffective, capable of driving the cell only when stimulated electrically and thus carrying a synchronous volley from a number of highly convergent axons. The contribution of this secondary afferent channel to normal and pathological cord physiology has now to be determined.     

Simple reaction time to cutaneous temperature stimuli.

Describes an apparatus that permits the measurement of simple RT to temperatures applied to the skin. 3 above-normal temperatures and 3 below-normal skin temperatures were used. The RT to touch was also obtained. Ss were 6 male and 6 female undergraduates. RT to cold was significantly faster at each temperature than RT to warm. The relevance of these results to contemporary theory of thermal sensitivity is discussed. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dorsal horn projection targets of ON and OFF cells in the rostral ventromedial medulla

1. The rostral ventromedial medulla (RVM) participates in the modulation of nociceptive transmission by spinal cord neurons. Previous anatomic studies have demonstrated that RVM neurons project to laminae I, II, and V of the dorsal horn; laminae VII and VIII of the intermediate and ventral horns; the intermediolateral column; and lamina X. The RVM contains at least three physiologically defined classes of neurons, two of which, the ON and the OFF cells, have been implicated in nociceptive modulation. Because these cells classes are intermingled in the RVM, it has not been possible to determine the spinal laminar projection targets of ON and OFF cells by anatomic methods. Therefore in the current study we employed antidromic microstimulation methods to determine the laminar projections of two of the three classes of RVM neurons, the ON and the OFF cells. 2. In lightly anesthetized (with methohexital sodium) rats, single-unit extracellular recordings were made from 48 RVM neurons that were physiologically characterized as ON (30) or OFF (18) cells. The recording locations of 45 of these neurons were recovered. Thirty-seven were found in the nucleus raphe magnus and eight were located near its dorsal and lateral borders. 3. Thirty-two physiologically identified RVM neurons (18 ON and 14 OFF cells) were antidromically activated from the cervical spinal cord using a monopolar stimulating electrode. The stimulating electrode was moved systematically in the white matter until antidromic activation could be produced with currents of < or = 20 microA (6.1 +/- 0.7 microA, mean +/- SE). The points from which minimum currents were required to antidromically activate the neurons were located mainly in the ipsilateral dorsolateral funiculus (DLF) (27 of 32). In a few cases, lowest antidromic threshold currents were found near the border between the DLF and ventrolateral funiculus (VLF) or, rarely, in the VLF itself. In these cases, the cell recordings were found to be near the dorsal boundary of the RVM. 4. While one electrode was used to stimulate the parent axon in the lateral funiculus, a second was used to explore the gray matter for the presence of collateral branches. The identification of a branch was initially determined by an increase in antidromic latency. At the same rostrocaudal plane of the spinal cord, stimulation of the DLF induced an antidromic spike that invaded the neuron earlier than the antidromic spike elicited by stimulation in the gray matter. Collateral branches were confirmed by establishing that the location of the minimum threshold point for antidromic activation of the neurons from the second electrode was in the gray matter, that the minimum current required to antidromically activate the neuron from that point was too low to activate the parent axon in the DLF, and that a collision occurred between the spikes induced by the two stimulating electrodes. 5. In 17 cases, physiologically identified RVM neurons (10 ON and 7 OFF cells) were antidromically activated from the gray matter of the cervical spinal cord using a current of 8.4 +/- 2.1 (SE) microA. Minimum threshold points for antidromic activation were found in laminae I-II (3 ON and 4 OFF cells), lamina V (5 ON and 6 OFF cells), and regions ventral to the lateral reticulated area (3 ON and 2 OFF cells) of the gray matter. As indicated by these numbers, some neurons were antidromically activated from more than one gray matter region. In general, all OFF cells and 9 of 10 ON cells were antidromically activated from low threshold points in either laminae I-II or lamina V. 6. In six cases, neurons were activated from separate points located in two or three different laminae of the gray matter. Three OFF cells were activated from laminae I-II and V, one OFF cell and one ON cell were activated from lamina V and from more ventral points, and one ON cell was activated from laminae I-II and from points ventral to lamina V.     

Sequence effects in categorization of simple perceptual stimuli.

Categorization research typically assumes that the cognitive system has access to a (more or less noisy) representation of the absolute magnitudes of the properties of stimuli and that this information is used in reaching a categorization decision. However, research on identification of simple perceptual stimuli suggests that people have very poor representations of absolute magnitude information and that judgments about absolute magnitude are strongly influenced by preceding material. The experiments presented here investigate such sequence effects in categorization tasks. Strong sequence effects were found. Classification of a borderline stimulus was more accurate when preceded by a distant member of the opposite category than by a distant member of the same category. It is argued that this category contrast effect cannot be accounted for by extant exemplar or decision-bound models of categorization. The effect suggests the use of relative magnitude information in categorization. A memory and contrast model illustrates how relative magnitude information may be used in categorization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What do misestimations and asymmetries in spatial judgement indicate about spatial representation?

When people are asked to judge the distance between 2 points, they may produce systematic over- or underestimations. Their judgements may also show asymmetries, as when, for example, people estimate the distance from their house to a mailbox as different from the distance from the mailbox to their house. It has been argued that such errors show that spatial representations are fundamentally nonmetric. In 3 experiments, however, the authors show that these effects can be explained by a category-adjustment (CA) model of spatial coding, in which coding is hierarchical (i.e., occurs at more than one level of measurement, with estimates based on combination across levels). In this model, coding at each level is uncertain but not distorted. Experiment 1 shows that, in a carefully controlled experimental setting, the CA model can be used to predict under- or overestimations of distances with respect to objective standards. Experiments 2 and 3 show that, when people learn maps, the CA model correctly predicts patterns of asymmetries in estimation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The indirect representation of sexual stimuli by schizophrenic and normal subjects.

"On the assumption that male schizophrenics are more threatened by various aspects of sexuality than are normal males, and that the prerecognition distortions of tachistoscopically presented sexual stimuli are often indirect representations reflecting the subject's immediate affective response to the stimulus object, it was hypothesized that a group of normal subjects could be differentiated from a group of schizophrenic subjects on the basis of the affective attitudes implied in the imagery of their respective prerecognition distortions. This hypothesis was tested by using an experimental group of 25 schizophrenic male subjects and a control group of 25 normal male subjects, with the groups equated for age, intelligence, ethnic group, and education." The hypothesis was, in general, supported by the data. From Psyc Abstracts 36:02:2JQ24A. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Fine grain of the neural representation of human spatial vision

It is widely held that in human spatial vision the visual scene is initially processed through visual filters, each of which is responsive to narrow ranges of image spatial frequencies. The physiological basis of these filters are thought to be cortical neurons with receptive fields of different sizes. The grain of the neural representation of spatial vision is much finer than had been supposed. Using laser interferometry, which effectively bypasses the demodulation of the optics of the eye, we measured discrimination of, and adaptation to, high spatial frequency laser interference fringe patterns. Spatial frequency discrimination was good right up to the visual resolution limit (average Weber fractions of 0.13 at 50 c/deg). Both contrast and spatial frequency matches made after adapting to extremely fine interference fringes strongly suggested that there existed even finer, relatively unadapted, filters (mechanisms with small receptive fields). The smallest cortical receptive fields processing spatial information in human vision are so small that they can possess receptive field centers hardly wider than single cone photoreceptors.     

The representation of auditory source characteristics: simple geometric form

Two experiments examined listeners' ability to discriminate the geometric shape of simple resonating bodies on the basis of their corresponding auditory attributes. In cross-modal matching tasks, subjects listened to recordings of pairs of metal bars (Experiment 1) or wooden bars (Experiment 2) struck in sequence and then selected a visual depiction of the bar cross sections that correctly represented their relative widths and heights from two opposing pairs presented on a computer screen. Multidimensional scaling solutions derived from matching scores for metal and wooden bars indicated that subjects' performance varied directly with increasing differences in the width/height (W/H) ratios of both sets of bars. Subsequent acoustic analyses revealed that the frequency components from torsional vibrational modes and the ratios of frequencies of transverse bending modes in the bars correlated strongly with both the bars' W/H ratios and bar coordinates in the multidimensional configurations. The results suggest that listeners can encode the auditory properties of sound sources by extracting certain invariant physical characteristics of their gross geometric properties from their acoustic behavior.     

Young children's representation of spatial information acquired from maps.

The early development of the ability to acquire integrated knowledge of a space from a map was investigated in 130 children, 4 to 7 years of age. Experiment 1 demonstrated that all 6- and 7-year-olds and many 4- and 5-year-olds could learn the layout of a large playhouse composed of six adjoined rooms by memorizing a map. Children who learned the map before entering the playhouse more quickly learned a route through it than children who were not exposed to the map, and older children performed significantly better than younger children. In Experiment 2 preschoolers learned a map of a space that contained six spatially separated small rooms within one large room. Children could therefore view the entire configuration of smaller rooms as they traveled around the larger room. Preschoolers performed significantly better in Experiment 2 than in Experiment 1, and the majority of them performed perfectly or almost perfectly. Taken together, the findings help to clarify young children's map-reading abilities in several respects and suggest that preschoolers' abilities are more substantial than has been assumed or demonstrated previously. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of 5-hydroxytryptamine and bradykinin in cat dorsal horn neurones activated by noxious stimuli

The levels of homovarillic acid and 3,4-dihydroxyphenylacetic acid in rat c. striatum after acute and 10 day administration of clozapine (30 and 100 mg/kg p.o.), thioridazine (100 mg/kg p.o.), haloperidol (1 mg/kg p.o.), and chlorpromazine (30 mg/kg p.o.), were estimated. With clozapine and haloperidol, the mesolimbic area was also investigated. With all these neuroleptics, the levels of both dopamine metabolites were reduced after a 10 day treatment as compared to acute administration, sometimes almost to control values. With clozapine, however, such a reduction occurred only with the higher dose of 100 mg/kg p.o., acting for a period longer than 24 h. This tolerance phenomenon was also observed with clozapine and haloperidol in the mesolimbic area. We conclude that clozapine is not qualitatively different from classical neuroleptics with respect to development of biochemical tolerance.     

Redistribution of spatial representation in the hippocampus of aged rats performing a spatial memory task.

Young and old rats performed on a maze according to a forced-choice and then a spatial memory procedure either in the same or a different environment. Aged rats were slower to learn the spatial memory task when tested in the same, but not in a different, room. One interpretation of this pattern of results is that although old rats learn new rules as quickly as young rats, they show less flexibility with old rules and familiar spatial information. Impaired choice accuracy during asymptote performance suggests poor processing of trial-unique information by old rats. Spatial correlates of hippocampal CA1 and hilar cells varied with task demand: CA1 cells of aged rats showed more spatially selective place fields, whereas hilar cells showed more diffuse location coding during spatial memory, and not forced-choice, tests. Such representational reorganization may reflect a compensatory response to age-related neurobiological changes in the hippocampus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Time perception in spatial neglect: A distorted representation?

Objective: It has been proposed that time, space, and numbers share the same metrics and cortical network, the right parietal cortex. Several recent investigations have demonstrated that the mental number line representation is distorted in neglect patients. The aim of this study is to investigate the relationship between time and spatial configuration in neglect patients. Method: Fourteen right-brain damaged patients (six with neglect and eight without neglect), as well as eight age-matched healthy controls, performed a time discrimination task. A standard tone (short: 700 ms and long: 1,700 ms) had to be confronted in duration to a test tone. Test tone differed of 100, 200, and 300 ms respect to the standard tone duration. Results: Neglect patients performed significantly worse than patients without neglect and healthy controls, irrespective of the duration of the standard tone. Conclusion: These results support the hypothesis that mental representations of space and time both share, to some extent, a common cortical network. Besides, spatial neglect seems to distort the time representation, inducing an overestimation of time durations. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Dorsal horn cells connected to the lissauer tract and their relation to the dorsal root potential in the rat

We have examined the role of dorsal horn cells that respond to Lissauer tract stimulation in regulating primary afferent depolarization (PAD). PAD was monitored by recording the dorsal root potential (DRP) in the roots of the lumbar cord. Recordings were made of the discharges of Lissauer tract-responsive cells, and their discharges were correlated with the DRPs occurring spontaneously and those evoked by stimulation. Electrical microstimulation of the Lissauer tract (<10 microA; 200 micros) was used to activate the tract selectively and evoke a characteristic long-latency DRP. Cells that were excited by Lissauer tract stimulation were found in the superficial laminae of the dorsal horn. They exhibited low rates of ongoing discharge and responded to Lissauer tract stimulation typically with a burst of impulses with a latency to onset of 5.6 +/- 2.7 ms (mean +/- SD) and to termination of 13.6 +/- 4.1 ms (n = 105). Lissauer tract-responsive cells in L5 were shown to receive convergent inputs from cutaneous and muscle afferents as they responded to stimulation of the sural nerve (100%, n = 19) and the nerve to gastrocnemius (95%, n = 19). The latency of the response to sural nerve stimulation was 3.7 +/- 1.5 ms and to gastrocnemius nerve stimulation, 8.3 +/- 3.6 ms. Stimulation through a microelectrode at a depth of 1.5 mm in the sensorimotor cortex (100 microA, 200 micros) evoked a response in 17 of 31 Lissauer tract-responsive cells (55%) with a latency to onset of 21.9 +/- 2.8 ms (n = 17). Stimulation of the sural nerve, nerve to gastrocnemius or sensorimotor cortex was shown to depress the response of Lissauer tract-responsive cells to a subsequent Lissauer tract stimulus. The ongoing discharges of Lissauer tract-responsive cells were correlated to the spontaneous DRP using spike-triggered averaging. Of 123 cells analyzed in this way, 117 (95%) were shown to be correlated to the DRP. In addition, the peaks of spontaneous negative DRPs in spinally transected animals were detected in software. Perievent time histograms triggered from these peaks showed the discharge of Lissauer tract-responsive cells to be correlated to the spontaneous DRPs in 57 of 62 cells (92%) recorded. We conclude that these data provide compelling evidence that the Lissauer tract, and the dorsal horn cells that it excites, mediate the PAD evoked from multiple neural pathways.     

Primitives used in the spatial localization of nonabutting stimuli: peaks or centroids

In order to determine whether simple luminance profiles are located by their peaks or centroids we performed a three element alignment task where the central element's degree of luminance asymmetry was randomly chosen from a flat distribution (skew noise). The central element with its randomly chosen skew was either positioned using the peak or centroid of its distribution. Accuracy is invariant with the magnitude of the skew noise for the centroid but not the peak condition. We conclude that the human visual system assigns position tags using centroids not peaks of luminance distributions for gabors. However this is not the case for Gaussian blobs, where a measure closer to the midpoint is used for our stimulus arrangement.     

Gender differences in horizontality and verticality representation in relation to initial position of the stimuli.

Examined the relationship between self-evaluation of movement imagery and performance under the standard format of the water-level (WL) and plumb-line (PL) tasks by evaluating a possible connection between vividness of such imagery and a propensity to spontaneously infer that stimuli are either still or moving when making the drawings. 126 female and 69 male college students (aged 17–45 yrs) were submitted either to the modified, static presentation of the WL task or to the standard, dynamic format using both upright and tilted positions. Ss were also submitted to corresponding PL tasks requiring verticality representation. In addition, they rated the vividness of their movement imagery. Women's proficiency was not higher under the static format of the WL and PL tasks. However, as expected, men's achievement was independent from presentation format. Men surpassed women under both static and dynamic formats. Finally, performance was not correlated with movement imagery. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cues that hippocampal place cells encode: dynamic and hierarchical representation of local and distal stimuli

Hippocampal place fields were recorded as rats explored a four-arm radial maze surrounded by curtains holding distal stimuli and with distinct local tactile, olfactory, and visual cues covering each arm. Systematic manipulations of the individual cues and their interrelationships showed that different hippocampal neurons encoded individual local and distal cues, relationships among cues within a stimulus set, and the relationship between the local and distal cues. Double rotation trials, which maintained stimulus relationships within distal and local cue sets, but altered the relationship between them, often changed the responses of the sampled neural population and produced new representations. After repeated double rotation trials, the incidence of new representations increased, and the likelihood of a simple rotation with one of the cue sets diminished. Cue scrambling trials, which altered the topological relationship within the local or distal stimulus set, showed that the cells that followed one set of controlled stimuli responded as often to a single cue as to the constellation. These cells followed the single cue when the stimulus constellation was scrambled, but often continued firing in the same place when the stimulus was removed or switched to respond to other cues. When the maze was surrounded by a new stimulus configuration, all of the cells either developed new place fields or stopped firing, showing that the controlled stimuli had persistent and profound influence over hippocampal neurons. Together, the results show that hippocampal neurons encode a hierarchical representation of environmental information.     

Effects of attending selectively to the spatial position of reflex-eliciting and reflex-modulating stimuli.

The question of whether automatic, sensory processes can be modified by selectively directing attention to stimuli was addressed by comparing effects on brainstem reflexes that share a common efferent pathway but have distinct afferent limbs. Subjects judged the duration of brief but intense blink-eliciting tones (Experiment 1) or weak tones preceding a blink-eliciting air puff at interstimulus intervals producing blink inhibition (Experiment 2). Tones occurred unpredictably at left, right, or midline loci; designation of the target location varied across blocks of trials. Latency of blinks to lateralized blink-eliciting targets was facilitated selectively, and the magnitude of blinks evoked by air puff following lateralized prestimulus targets was inhibited selectively. There was no evidence for a midline selective effect. Results appear to support a preset differential processing of stimuli in sensory pathways at low, possibly subcortical, levels and the consequent modification of obligatory, automatic processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tactile perception of spatial stimuli on the lip surface by young and older adults

Although older adults are subject to both subtle changes and major disorders of the oral sensorimotor system, relatively little is known about oral sensory function in old age. Accurate assessment of oral tactile perception is needed to document disability, aid prognosis, and plan treatment for older adults with disorders affecting speech or feeding. However, normative information currently available for older adults is mainly based on two-point discrimination, a problematic measure of tactile spatial resolution. Grating orientation discrimination, a technique developed to provide a clear and reliable measure of spatial resolution, was used to test sensitivity of the upper and lower lip vermillion, on right and left sides, in a sample of 40 young adults and 40 adults age 66-85. Results indicated that spatial acuity at the lip vermilion declines significantly in old age and that women tend to have better acuity than men. No significant differences were found in acuity between the upper and lower lips or between right and left sides for either age group. Peripheral changes in receptor density and lip tissue composition are suggested as likely causes for the age-related decline.     

Allocation of spatial attention to emotional stimuli depends upon arousal and not valence.

Attentional allocation to emotional stimuli is often proposed to be driven by valence and in particular by negativity. However, many negative stimuli are also arousing leaving the question whether valence or arousal accounts for this effect. The authors examined whether the valence or the arousal level of emotional stimuli influences the allocation of spatial attention using a modified spatial cueing task. Participants responded to targets that were preceded by cues consisting of emotional pictures varying on arousal and valence. Response latencies showed that disengagement of spatial attention was slower for stimuli high in arousal than for stimuli low in arousal. The effect was independent of the valence of the pictures and not gender-specific. The findings support the idea that arousal affects the allocation of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)