Albert Postma

Detection of errors during speech production : a review of speech monitoring models

In this paper three theories of speech monitoring are evaluated. The perception-based approach proposes that the same mechanism employed in understanding other-produced language, the speech comprehension system, is also used to monitor ones own speech production. A conceptual, an inner, and an auditory loop convey information to a central, conscious monitor which scrutinizes the adequacy of the ongoing speech flow. In this model, only the end-products in the speech production sequences, the preverbal (propositional) message, the phonetic plan, and the auditory results, are verified. The production-based account assumes multiple local, autonomous monitoring devices, which can look inside formulation components. Moreover, these devices might be tuned to various signals from the actual speech motor execution, e.g. efferent, tactile, and proprioceptive feedback. Finally, node structure theory views error detection as a natural outflow of the activation patterns in the node system for speech production. Errors result in prolonged activation of uncommitted nodes, which in turn may incite error awareness. The approaches differ on the points of consciousness, volition and control, the number of monitoring channels, and their speed, flexibility, and capacity, and whether they can account for concurrent language comprehension disorders. From the empirical evidence presently available, it is argued for a central perception-based monitor, potentially augmented with a few automatic, production-based error detection devices.

On the hemispheric specialization for categorical and coordinate spatial relations: a review of the current evidence

This article reviews current evidence on the hemispheric specialization hypothesis for two types of spatial relations representations; categorical versus coordinate [Psychol. Rev. 94 (1987) 148; J. Exp. Psychol.: Percept. Perform. 15 (1989) 723]. Categorical representations capture general properties of the spatial structure of a visual stimulus, without defining the exact metric properties. Coordinate representations specify precise spatial locations of objects or parts in terms of metric units. It is claimed that a hemispheric difference in contribution to the computation of both types of spatial relations representations exists, in which the left hemisphere is specialized for the computation of categorical spatial representations while the right hemisphere is specialized for the computation of coordinate ones. Several forms of research (experimental, computer simulations, patient studies and neuroimaging studies) are reviewed. In general, there is convergent evidence for a conceptual separation of coordinate and categorical processing, with strongest indications for a relative right hemisphere advantage in encoding coordinate spatial relations, and weaker support for left hemispheric categorical specialization. The pattern appears to be critically linked to receptive field properties of the two hemispheres and as such is modulated by certain elementary visual characteristics of the displayed stimuli.

Varieties of human spatial memory : a meta-analysis on the effects of hippocampal lesions

The current meta-analysis included 27 studies on spatial-memory dysfunction in patients with hippocampal damage. Each study was classified on the basis of the task that was used, i.e., maze learning, working memory, object-location memory, or positional memory. The overall results demonstrated impairments on all spatial-memory tasks. Clear differences in effect size were found between positional memory on the one hand and maze learning, object-location memory, and working memory on the other hand. Lateralization was found only on maze learning and object-location memory. These findings clearly indicate that specific aspects of spatial memory can be affected in various degrees in patients with hippocampal lesions. Moreover, these results strongly support the notion that the hippocampus is important in the processing of metric positional information, probably in the form of an allocentric cognitive map.

Gender differences in object location memory: A meta-analysis

The goal of the present study was to quantify the magnitude of gender differences in object location memory tasks. A total of 123 effect sizes (d ) drawn from 36 studies were included in a meta-analysis using a hierarchical approach. Object identity memory (37 effect sizes) and object location memory (86 effect sizes) tasks were analyzed separately. Object identity memory task showed significant gender differences that were homogeneous and in favor of women. For the object location memory tasks, effect sizes had to be partitioned by age (younger than 13, between 13 and 18, older than 18), object type (common, uncommon, gender neutral, geometric, masculine, feminine), scoring method (accuracy, time, distance), and type of measure (recall, recognition) to achieve homogeneity. Significant gender differences in favor of females were obtained in all clusters above the age of 13, with the exception of feminine, uncommon, and gender-neutral objects. Masculine objects and measures of distance produced significant effects in favor of males. Implications of these results for future work and for theoretical interpretations are discussed.

Sex differences for selective forms of spatial memory

In the present study, a systematic comparison of sex differences for several tests of spatial memory was conducted. Clear evidence for more accurate male performance was obtained for precise metric positional information in a wayfinding task and in an object location memory task. In contrast, no sex difference characterized topological information processing (object-to-position assignment). Together, these findings provide further insight in the specificity of sex differences in spatial memory and in the functional architecture of spatial memory. Implications for the relevant evolutionary basis are discussed.

What Was Where? Memory for Object Locations

Three experiments are reported on short-term memory for object location. Stimulus displays containing different numbers and types of objects were presented for 30 seconds, after which subjects were required to relocate the various objects within the display, merely to reconstruct positions, or to assign objects correctly to an equal number of premarked positions. In all experiments half the trials were performed with concurrent articulatory suppression. The results support the hypothesis that two processes can be distinguished: one that underlies the construction of a positional map and one that assigns objects to positions. These processes are differentially affected by object numbers and articulatory suppression. This hypothesis is discussed in terms of Baddeleys (1986) working memory model and Kosslyns (1987) distinction between “categorical” and “coordinate” spatial relations.

Laterality effects in selective attention to threat after repetitive transcranial magnetic stimulation at the prefrontal cortex in female subjects

Recently, several experiments have indicated that the left and right prefrontal cortex (PFC) are differently involved in emotional processing. The aim of this study was to investigate the role of the left and right PFC in selective attention to angry faces by using a pictorial emotional Stroop task. Slow repetitive transcranial magnetic stimulation (rTMS) was applied to the left and right PFC of 10 female subjects for 15 min on separate days. Results showed a significant effect of stimulation position: right PFC rTMS resulted in selective attention towards angry faces, whereas left PFC rTMS resulted in selective attention away from angry faces. This finding is in accordance with theoretical accounts of the neural implementation of approach and withdrawal systems.

Effects of slow rTMS at the right dorsolateral prefrontal cortex on EEG asymmetry and mood.

In a sham-controlled design (n = 12), slow repetitive transcranial magnetic stimulation (rTMS) was applied to the right dorsolateral prefrontal cortex for 20 min, and the subsequent effects on mood and the EEG spectrum were investigated. Analysis revealed a significant left hemisphere increase in EEG theta activity at 25–35 and 55–65 min after stimulation. In addition, participants reported significant decrease in anxiety immediately after stimulation, as well as 35 and 65 min after rTMS. These findings indicate that reductions in anxiety after slow rTMS at the right dorsolateral prefrontal cortex are associated with a contralateral increase in theta activity.

Effects of testosterone administration on selective aspects of object-location memory in healthy young women

Previous work has indicated that object-location memory is sensitive to sex differences as well as variations in the menstrual cycle. The goal of the present study was to further examine the hormonal basis of human spatial memory by assessing the effects of a single dose of exogenous testosterone in healthy young women on three recall conditions: positional reconstruction; object-to-position-assignment; and the combined condition in which subjects both have to reconstruct the precise locations and to link the different objects to the correct places. In the latter condition, delayed recall (3 min delay) improved with testosterone. Although the effects were only small and need further substantiation, they support the idea that testosterone may have an activational effect on selective aspects of cognitive functioning.

Interactions between ego- and allocentric neuronal representations of space

In the primate brain, visual spatial representations express distances of objects with regard to different references. In the parietal cortex, distances are thought to be represented with respect to the body (egocentric representation) and in superior temporal cortices with respect to other objects, independent of the observer (allocentric representation). However, these representations of space are interdependent, complicating such distinctions. Specifically, an objects position within a background frame strongly biases egocentric position location judgments. This bias, however, is absent for pointing movements towards that same object. More recent theories state that dorsal parietal spatial representations subserve visuomotor processing, whereas temporal lobe representations subserve memory and cognition. Therefore, it may be hypothesized that parietal egocentric representations, responsible for movement control, are not influenced by irrelevant allocentric cues, whereas ventral representations are. In an event-related functional magnetic resonance imaging study, subjects judged target bar locations relative to their body (egocentric task) or a background bar (allocentric task). Activity in the superior parietal lobule (SPL) was shown to increase during egocentric judgments, but not during allocentric judgments. The superior temporal gyrus (STG) shows a negative BOLD response during allocentric judgments and no activation during egocentric judgments. During egocentric judgments, the irrelevant background influenced activity in the posterior commissure and the medial temporal gyrus. SPL activity was unaffected by the irrelevant background during egocentric judgments. Sensitivity to spatial perceptual biases is apparently limited to occipito-temporal areas, subserving the observed biased cognitive reports of location, and is not found in parietal areas, subserving unbiased goal-directed actions.