Patricia A. Carpenter’s research while affiliated with Carnegie Mellon University and other places

This paper describes and provides support for a non-representational theory of perception called the Fractal Catalytic theory, which proposes that perception is a catalytic type of process that occurs at multiple scales.1 Enzyme catalysis involves a vibratory facilitation of a reaction. A catalytic model for smell at the molecular level is supported by evidence that smell involves a vibratory process.2 This type of facilitation can be generalized to the neural level, where many neuroscientists have observed vibratory neural patterns. At the level of the organism, we describe research with blind individuals who experience a visuo-spatial world through patterns of sounds or tactile vibrations. Such research argues against the standard theory that people are representing objects and events, and supports the view that experience arises as an organism mediates (catalyzes) the transitions in its surround. The theory relates to the biologically-grounded theory of Autopoiesis3 as well as proposals that catalysis is central in biological evolution. We examine the implications of this theory for the nature of consciousness.

This study uses fMRI (functional magnetic resonance imaging) to investigate the brain activity in a set of cortical areas in the task of main idea identification, when the topic sentence was presented in first versus in last position in a three-sentence paragraph. The participants were eight right-handed undergraduate students from Carnegie Mellon University, six male and 2 female, all native speakers of English. Each participant read twelve paragraphs, six in which the topic sentence was paragraph initial and six in which it was paragraph final, and each paragraph was presented word by word in the center of a screen, inside the scanner. The major finding of the current study is the differential response observed in the left and right hemispheres as to the location of the topic sentence within the paragraph. The left temporal region showed greater activation when the topic sentence was in final position than in initial position. The right temporal region, on the other hand, was affected only by sentence type, showing a greater response to topic sentences than support sentences, regardless of their location within the paragraph.

Verbal and spatial working memory were examined in high-functioning children, adolescents, and adults with autism compared to age and cognitive-matched controls. No deficit was found in verbal working memory in the individuals with autism using an N-back letter task and standardized measures. The distinction between the N-back task and others used previously to infer a working memory deficit in autism is that this task does not involve a complex cognitive demand. Deficits were found in spatial working memory. Understanding the basis for the dissociation between intact verbal working memory and impaired spatial working memory and the breakdown that occurs in verbal working memory as information processing demands are increased will likely provide valuable insights into the neural basis of autism.

In this fMRI study, we examined the relationship between activations in the inferotemporal region (ventral pathway) and the parietal region (dorsal pathway), as well as in the prefrontal cortex (associated with working memory), in a modified mental rotation task. We manipulated figural complexity (simple vs. complex) to affect the figure recognition process (associated with the ventral pathway) and the amount of rotation (0 degrees vs. 90 degrees), typically associated with the dorsal pathway. The pattern of activation not only showed that both streams are affected by both manipulations, but also showed an overadditive interaction. The effect of figural complexity was greater for 90 degrees rotation than for 0 degrees in multiple regions, including the ventral, dorsal, and prefrontal regions. In addition, functional connectivity analyses on the correlations across the time courses of activation between regions of interest showed increased synchronization among multiple brain areas as task demand increased. The results indicate that both the dorsal and the ventral pathways show interactive effects of object and spatial processing, and they suggest that multiple regions interact to perform mental rotation.

An fMRI study was used to measure the brain activation of a group of adults with high-functioning autism compared to a Full Scale and Verbal IQ and age-matched control group during an n-back working memory task with letters. The behavioral results showed comparable performance, but the fMRI results suggested that the normal controls might use verbal codes to perform the task, while the adults with autism might use visual codes. The control group demonstrated more activation in the left than the right parietal regions, whereas the autism group showed more right lateralized activation in the prefrontal and parietal regions. The autism group also had more activation than the control group in the posterior regions including inferior temporal and occipital regions. The analysis of functional connectivity yielded similar patterns for the two groups with different hemispheric correlations. The temporal profile of the activity in the prefrontal regions was more correlated with the left parietal regions for the control group, whereas it was more correlated with the right parietal regions for the autism group.

This study examined brain activation while participants read or listened to high-imagery sentences like The number eight when rotated 90 degrees looks like a pair of spectacles or low-imagery sentences, and judged them as true or false. The sentence imagery manipulation affected the activation in regions (particularly, the intraparietal sulcus) that activate in other mental imagery tasks, such as mental rotation. Both the auditory and visual presentation experiments indicated activation of the intraparietal sulcus area in the high-imagery condition, suggesting a common neural substrate for language-evoked imagery that is independent of the input modality. In addition to exhibiting greater activation levels during the processing of high-imagery sentences, the left intraparietal sulcus also showed greater functional connectivity in this condition with other cortical regions, particularly language processing regions, regardless of the input modality. The comprehension of abstract, nonimaginal information in low-imagery sentences was accompanied by additional activation in regions in the left superior and middle temporal areas associated with the retrieval and processing of semantic and world knowledge. In addition to exhibiting greater activation levels during the processing of low-imagery sentences, this left temporal region also revealed greater functional connectivity in this condition with other left hemisphere language processing regions and with prefrontal regions, regardless of the input modality. The findings indicate that sentence comprehension can activate additional cortical regions that process information that is not specifically linguistic but varies with the information content of the sentence (such as visual or abstract information). In particular, the left intraparietal sulcus area appears to be centrally involved in processing the visual imagery that a sentence can evoke, while activating in synchrony with some core language processing regions.

Two fMRI studies investigated the time course and amplitude of brain activity in language-related areas during the processing of syntactically ambiguous sentences. In Experiment 1, higher levels of activation were found during the reading of unpreferred syntactic structures as well as more complex structures. In Experiments 2A and 2B higher levels of brain activation were found for ambiguous sentences compared with unambiguous sentences matched for syntactic complexity, even when the ambiguities were resolved in favor of the preferred syntactic construction (despite the absence of this difference in previous reading time results). Although results can be reconciled with either serial or parallel models of sentence parsing, they arguably fit better into the parallel framework. Serial models can admittedly be made consistent but only by including a parallel component. The fMRI data indicate the involvement of a parallel component in syntactic parsing that might be either a selection mechanism or a construction of multiple parses.

The project research is completed. Several manuscripts are still in the process of being prepared for publication. The project has developed paradigms to study high-level, high-demand cognitive tasks with fMRI. The project has discovered a surprising phenomenon regarding a mutual constraint on the total amount of cortical activation possible in a dual task situation. The project has determined the effects of input modality in dual tasking. The project has developed an experimental control system (CogLab NT) that will enable future fMRI investigation of the performance of dynamic tasks with some of the critical properties of high-information-load STE's. The project has developed paradigms to study high-level, high-demand dynamic cognitive tasks behaviorally. The project has developed brain-based measures of cognitive workload. The project has developed a theory of learning in dynamic decision environments, called Instance-Based Learning Theory (IBLT).