Scielo RSS <![CDATA[Biological Research]]> vol. 41 num. 4 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<strong>A tribute to Dr. Teresa Pinto-Hamuy</strong>]]> <![CDATA[<strong>The parietal association cortex of the rat</strong>]]> Spatial cognition is a complex higher function in mammals and is involved in a variety of tasks that can be explored in the laboratory. In this review we will discuss the role of the posterior parietal/anteromedial cortex of rodents, also known as the parietal association cortex, and the hippocampal formation in spatial navigation. We will also discuss other higher associational functions of the posterior parietal/anteromedial cortex as they relate to Dr. Pinto-Hamuy's contribution to understanding behavioral functions. <![CDATA[<strong>Olfactory or auditory stimulation and their hedonic valúes differentially modulate visual working memory</strong>]]> Working memory (WM) designates the retention of objects or events in conscious awareness when these are not present in the environment. Many studies have focused on the interference properties of distracter stimuli in working memory, but these studies have mainly examined the influence of the intensity of these stimuli. Little is known about the memory modulation of hedonic content of distracter stimuli as they also may affect WM performance or attentional tasks. In this paper, we have studied the performance of a visual WM task where subjects recollect from five to eight visually presented objects while they are simultaneously exposed to additional - albeit weak- auditory or olfactory distracter stimulus. We found that WM performance decreases as the number of Ítems to remember increases, but this performance was unaltered by any of the distracter stimuli. However, when performance was correlated to the subject's perceived hedonic valúes, distracter stimuli classified as negative exhibit higher error rates than positive, neutral or control stimuli. We demónstrate that some hedonic content of otherwise neutral stimuli can strongly modulate memory processes. <![CDATA[<strong>Measuring emotion in the voice during psychotherapy interventions</strong>: <strong>Apilot study</strong>]]> The voice as a representation of the psychic world of patients in psychotherapeutic interventions has not been studied thoroughly. To explore speech prosody in relation to the emotional content of words, voices recorded during a semi-structured interview were analyzed. The subjects had been classified according to their childhood emotional experiences with caregivers and their different attachment representations. In this pilot study, voice quality as spectral parameters extracted from vowels of the key word "mother" (Germán: "Mutter") were analyzed. The amplitude of the second harmonic was large relative to the amplitude of the third harmonic for the vowel "u" in the secure group as compared to the preoccupied group. Such differences might be related to the subjects' emotional involvement during an interview eliciting reconstructed childhood memories. <![CDATA[<strong>Long lasting structural changes in primary motor cortex after motor skill learning</strong>: <strong>a behavioural and stereological study</strong>]]> Many motor skills, once acquired, are stored over a long time period, probably sustained by permanent neuronal changes. Thus, in this paper we have investigated with quantitative stereology the generation and persistence of neuronal density changes in primary motor cortex (MI) following motor skill learning (skilled reaching task). Rats were trained a lateralised reaching task during an "early" (22-31 days oíd) or "late" (362-371 days oíd) postnatal period. The trained and corresponding control rats were sacrificed at day 372, immediately after the behavioural testing. The "early" trained group preserved the learned skilled reaching task when tested at day 372, without requiring any additional training. The "late" trained group showed a similar capacity to that of the "early" trained group for learning the skilled reaching task. All trained animáis ("early" and "late" trained groups) showed a significant Ínter hemispheric decrease of neuronal density in the corresponding motor forelimb representation área of MI (cortical layers II-III) <![CDATA[<strong>The anteromedial extrastriate complex is critical for the use of allocentric visual cues and in the retention of the Lashley III maze task in rats</strong>]]> The anteromedial extrastriate complex has been proposed to play an essential role in a spatial orientation system in rats. To gain more information about that possible role, in the present work, two questions were addressed: 1. Are allocentric visual cues relevant for acquisition of the orientation task in the Lashley III maze? 2. Is this integration of allocentric inputs in the anteromedial visual complex relevant in the retention of this test? While a control group of rats was trained keeping the maze in the same position, the experimental group was trained with the maze rotated counterclockwise by 144 degrees from session to session. Control rats reached learning criterion significantly earlier and with less errors than the experimental ones (p<.05). After 11 sessions, rats of both groups received stereotaxic injections of ibotenic acid in the anteromedial complex. In the retention test one week after surgery, the control group, which had been able to learn using egocentric and allocentric visual cues, showed a greater déficit than the experimental animáis (p<.05). These results confirm the role of the anteromedial complex in the processing of visuospatial orientation tasks and demónstrate the integration of allocentric visual cues in the solution of those tasks. <![CDATA[<strong>Topography and axon arbor architecture in the visual callosal pathway</strong>: <strong>effects of deafferentation and blockade of TV-methyl-D-aspartate receptors</strong>]]> Visual callosal fibers link cortical loci in opposite hemispheres that represent the same visual field but whose locations are not mirror-symmetric with respect to the brain midline. Presence of the eyes from postnatal day 4 (P4) to P6 is required for this map to be specified. We tested the hypothesis that specification of the callosal map requires the activation of A'-methyl-D-aspartate receptors (NMDARs). Our results show that blockade of NMDARs with MK-801 during this critical period did not induce obvious abnormalities in callosal connectivity patterns, suggesting that retinal influences do not opérate through NMDAR-mediated processes to specify normal callosal topography. In contrast, we found that interfering with NMDAR function either through MK801-induced blockade of NMDARs starting at P6 or neonatal enucleation significantly increases the length of axon branches and total length of arbors, without major effects on the number of branch tips. Our results further suggest that NMDARs act by altering the initial elaboration of arbors rather than by inhibiting a later-occurring remodeling process. Since the callosal map is present by P6, just as axonal branches of simple architecture grow into gray matter, we suggest that regulation of arbor development by NMDAR-mediated processes is important for maintaining the precisión of this map. <![CDATA[<strong>Plasticity in primary somatosensory cortex resulting from environmentally enriched stimulation and sensory discrimination training</strong>]]> We studied primary-somatosensory cortical plasticity due to selective stimulation of the sensory periphery by two procedures of active exploration in adult rats. Subjects, left with only three adjacent whiskers, were trained in a roughness discrimination task or maintained in a tactile enriched environment. Either training or enrichment produced 3-fold increases in the barrel cortex áreas of behaviorally-engaged whisker representations, in their zones of overlap. While the overall áreas of representation expanded dramatically, the domains of exclusive principal whisker responses were virtually identical in enriched vs normal rats and were significantly smaller than either group in roughness discrimination-trained rats. When animáis were trained or exposed to enriched environments with the three whiskers arrayed in an are or row, very equivalent overlaps in representations were recorded across their greatly-enlarged whisker representation zones. This equivalence in distortion in these behavioral preparations is in contradistinction to the normal rat, where overlap is strongly biased only along rows, probably reflecting the establishment of different relations with the neighboring cortical columns. Overall, plasticity phenomena are argued to be consistent with the predictions of competitive Hebbian network plasticity. <![CDATA[<strong>On-line analysis of biosignals for the automation of total and specific sleep deprivation in the rat</strong>]]> A computer-based system that automates sleep studies, including sleep deprivation paradigms, is described. The system allows for total or REM-specific sleep deprivation and is based on a reliable, fast-responding, on-line state detection algorithm linked to a dependable intervention device. Behavioral state detection is achieved by dimensión reduction of short-term EEG power spectrum. Interventions are made by serial outputs to servomotors that move a cage with different patterns and variable intensity. The system can adapt itself to individual characteristics and to changes in recording conditions. Customized protocols can be designed by defining the states or stages to be deprived, including scheduling temporal patterns. A detailed analysis of the relevant signáis during and after deprivation is readily available. Data is presented from two experimental designs in rats. One consisted of specific REM-sleep short-term deprivation and the other of 10-hour total sleep deprivation. An outline of conceptual and practical considerations involved in the automation of laboratory set-ups oriented to biosignal analysis is provided. Careful monitoring of sleep EEG variables during sleep deprivation suggests peculiarities of brain functioning in that condition. A corollary is that sleep deprivation should not be considered to be merely a forced prolonged wakefulness. <![CDATA[<strong>Voluntary modulations of attention in a semantic auditory-visual matching Task</strong>: <strong>an ERP study</strong>]]> The present study explores the neural correlates of voluntary modulations of attention in an auditory-visual matching task. Visual stimuli (a female or a male face) were preceded in cióse temporal proximity by auditory stimuli consisting of the Spanish word for "man" and "woman" ("hombre" or "mujer"). In 80% of the triáis the gender of the two stimuli coincided. Participants were asked to mentally count the specific instances in which a female face appeared after hearing the word "man" (10 % of the triáis). Our results show attention-related amplitude modulation of the early visual ERP components NI and anterior P2, but also amplitude modulations of (i) the N270 potential usually associated with conflict detection, (ii) a P300 wave related to infrequency, and (iii) an N400 potential related to semantic incongruence. The elicitation of these latter components varied according to task manipulations, evidencing the role of voluntary allocation of attention in fine-tuning cognitive processing, which includes basic processes like detection of infrequency or semantic incongruity often considered to be volition-independent. <![CDATA[<strong>Non-homogeneous spatial configuration of vibrissae cortical representation in layer IV of the barrel somatosensory cortex</strong>]]> In the present experiments we studied exclusive and overlapping cortical representational áreas of the vibrissae in layer IV cells, across the entire barrel subfield of the rat somatosensory cortex, looking for evidences that would challenge the present assumptions of homogeneity and symmetry among cortical columns in this sensorial system. Our main findings were that in layer IV of the rat barrel cortex: A) Size of vibrissae cortical representational áreas (X=0.4174mm²; SD=0.025) was not homo geneous, vibrissae in dorsal rows (A-B) had significantly smaller áreas than those in ventral rows (D-E), a pattern that repeated itself in ares 1-4. B) This difference arises from vibrissal representational overlap, and not from variations in exclusive zones, which are surprisingly homogeneous in size across the barrel cortex (X=0.079mm²; SD=0.0075); C) The extent of overlapping cortical áreas varied systematically, with intra-row overlapping áreas having a predominant bias (71.4% of total overlapping) independent of área sizes. Accordingly, vibrissae shared receptive fields with an average of 1.15 vibrissae in the same row and 0.38 in the same are. Barrel cortex has been viewed operationally as a conglomérate of essentially homogenous cortical columns that interact equivalently in the are and row dimensions. Our simple but global cortical reconstructions show that this predominant view should be revised. We postúlate that the vibrissae/barrels spatial disposition in rows and ares has a relevant functional meaning, related to different sensory capabilities. <![CDATA[<strong>A neutral cue facilitates detection of a visual target by modulating attention</strong>]]> Twelve rats were trained to perform a two-choice visual detection task in which a right or left light was presented and the animáis were required to press the lever located under the illuminated light for a food reward. In seventy percent of the triáis the target light was preceded by presentation of a neutral cue (a central light). Relevance of the neutral cue for detection of the target was analyzed by comparing behavioral Índices of attention in its presence and absence. Accuracy was significantly higher in presence than in absence of the neutral cue, while mean response latencies were lower in presence than in absence of the neutral cue. These results indicate that the animáis allocated attentional resources on the target detection during a high expectancy period after the onset of the neutral cue. This could facilitate target detection and improve the performance in the presence of the neutral cue.