William M. Jenkins

Language Comprehension in Language-Learning Impaired Children Improved with Acoustically Modified Speech

A speech processing algorithm was developed to create more salient versions of the rapidly changing elements in the acoustic waveform of speech that have been shown to be deficiently processed by language-learning impaired (LLI) children. LLI children received extensive daily training, over a 4-week period, with listening exercises in which all speech was translated into this synthetic form. They also received daily training with computer “games” designed to adaptively drive improvements in temporal processing thresholds. Significant improvements in speech discrimination and language comprehension abilities were demonstrated in two independent groups of LLI children.

Temporal processing deficits of language-learning impaired children ameliorated by training.

Children with language-based learning impairments (LLIs) have major deficits in their recognition of some rapidly successive phonetic elements and nonspeech sound stimuli. In the current study, LLI children were engaged in adaptive training exercises mounted as computer “games” designed to drive improvements in their “temporal processing” skills. With 8 to 16 hours of training during a 20-day period, LLI children improved markedly in their abilities to recognize brief and fast sequences of nonspeech and speech stimuli.

Reorganization of neocortical representations after brain injury: a neurophysiological model of the bases of recovery from stroke.

Publisher Summary This chapter outlines the way somatosensory cortical maps of the skin surface are determined experimentally and summarizes some of the evidence for the functional plasticity of these somatosensory cortical representations of the skin surface in adults. The chapter describes new electrophysiological results that demonstrate that there is a functional reorganization of cortical representations of the skin surfaces in the cortical zones surrounding focal cortical lesions and considers some implications of these experiments for understanding cortical mechanisms underlying the behavioral recovery following brain injury. Somatosensory cortical representations of the skin surfaces in monkeys are remodeled by use throughout life by intrinsic input selection processes. Those processes are thought to underly learning, memory, and the acquisition of skill. In any event, there is a manifest plasticity of functional representational detail driven by use in cortical area, 3b, operating over distances of hundreds of microns in normal adult primates. It has been concluded that this functional map alterability does not involve a significant growth or movement of input terminal arbors, but rather, is accounted for by changes in the effectiveness of anatomically static inputs.

Reorganization of Cortical Representations of the Hand Following Alterations of Skin Inputs Induced by Nerve Injury, Skin Island Transfers, and Experience

Tactile experiences remodel the central nervous system representations of the body surface. The results of assessments of ten peripheral manipulations that reveal different aspects of representational plasticity are reviewed: (1) chronic peripheral denervation; (2) surgical amputation; (3) digital syndactyly and its natural behavioral equivalents; (4) peripheral nerve crush with reinnervation; (5) peripheral nerve transection and repair, with reinnervation; (6) denervation of very large skin surfaces, for very long times; (7) electrical stimulation of large-fiber afferents in the median nerve, simulating electroacupuncture; (8) implantation of always-innervated island pedicle flaps; (9) behavioral training with locationally invariant stimuli; and (10) behavioral training with moving stimuli. Focus is on the changes recorded in a primary somatosensory cortical field, area 3b, following these ten manipulations, in adult monkeys. On the basis of these findings, the following are discussed: (1) how altered schedules of activity from the skin contribute to cortical representational remodeling; (2) other factors that influence the representational remodeling; (3) where the remodeling actually occurs; and (4) some implications of these findings for sensory rehabilitation.

Language learning impairments: integrating basic science, technology, and remediation

Abstract One of the fundamental goals of the modern field of neuroscience is to understand how neuronal activity gives rise to higher cortical function. However, to bridge the gap between neurobiology and behavior, we must understand higher cortical functions at the behavioral level at least as well as we have come to understand neurobiological processes at the cellular and molecular levels. This is certainly the case in the study of speech processing, where critical studies of behavioral dysfunction have provided key insights into the basic neurobiological mechanisms relevant to speech perception and production. Much of this progress derives from a detailed analysis of the sensory, perceptual, cognitive, and motor abilities of children who fail to acquire speech, language, and reading skills normally within the context of otherwise normal development. Current research now shows that a dysfunction in normal phonological processing, which is critical to the development of oral and written language, may derive, at least in part, from difficulties in perceiving and producing basic sensory-motor information in rapid succession – within tens of ms (see Tallal et al. 1993a for a review).There is now substantial evidence supporting the hypothesis that basic temporal integration processes play a fundamental role in establishing neural representations for the units of speech (phonemes), which must be segmented from the (continuous) speech stream and combined to form words, in order for the normal development of oral and written language to proceed. Results from magnetic resonance imaging (MRI) and positron emission tomography (PET) studies, as well as studies of behavioral performance in normal and language impaired children and adults, will be reviewed to support the view that the integration of rapidly changing successive acoustic events plays a primary role in phonological development and disorders. Finally, remediation studies based on this research, coupled with neuroplasticity research, will be presented.

Neocortical representational dynamics in adult primates : implications for neuropsychology

Some evidence for functional reorganization of cortical somatosensory representations in adult primates is reviewed. These examples include representation remodeling in cortical area 3b following digit amputation, digit fusion, local intracortical microstimulation, restricted cortical lesions, or as a consequence of behaviorally controlled stimulation of restricted hand surfaces. We suggest that the profound changes in the cortical representations that have been observed after these and other manipulations must bear consequences for the specific behaviors that depend on the operation of this neural machinery. Furthermore, this lifelong dynamic cortical capacity for neuronal response adaptation by use almost certainly also underlies the progressive representational remodeling that we have recorded following brain lesions.

Experience-induced plasticity of cutaneous maps in the primary somatosensory cortex of adult monkeys and rats

In a first study, the representations of skin surfaces of the hand in the primary somatosensory cortex, area 3b, were reconstructed in owl monkeys and squirrel monkeys trained to pick up food pellets from small, shallow wells, a task which required skilled use of the digits. Training sessions included limited manual exercise over a total period of a few hours of practice. From an early clumsy performance in which many retrieval attempts were required for each successful pellet retrieval, the monkeys exhibited a gradual improvement. Typically, the animals used various combinations of digits before developing a successful retrieval strategy. As the behavior came to be stereotyped, monkeys consistently engaged surfaces of the distal phalanges of one or two digits in the palpation and capture of food pellets from the smallest wells. Microelectrode mapping of the hand surfaces revealed that the glabrous skin of the fingertips predominantly involved in the dexterity task was represented over topographically expanded cortical sectors. Furthermore, cutaneous receptive fields which covered the most frequently stimulated digital tip surfaces were less than half as large as were those representing the corresponding surfaces of control digits. In a second series of experiments, Long-Evans rats were assigned to environments promoting differential tactile experience (standard, enriched, and impoverished) for 80 to 115 days from the time of weaning. A fourth group of young adult rat experienced a severe restriction of forepaw exploratory movement for either 7 or 15 days. Cortical maps derived in the primary somatosensory cortex showed that environmental enrichment induced a substantial enlargement of the cutaneous forepaw representation, and improved its spatial resolution (smaller glabrous receptive fields). In contrast, tactile impoverishment resulted in a degradation of the forepaw representation that was characterized by larger cutaneous receptive fields and the emergence of non-cutaneous responses. Cortical maps derived in the hemispheres contralateral to the immobilized forelimb exhibited a severe decrease of about 50% in the overall areal extent of the cutaneous representation of the forepaw, which resulted from the invasion of topographically organized cortical zones of non-cutaneous responses, and numerous discontinuities in the representation of contiguous skin territories. The size and the spatial arrangement of the cutaneous receptive fields were not significantly modified by the immobilization of the contralateral forelimb. Similar results were obtained regardless of whether the forelimb restriction lasted 7 or 15 days. These two studies corroborate the view that representational constructs are permanently reshaped by novel experiences through dynamic competitive processes. These studies also support the notion that subject-environment interactions play a crucial role in the maintenance of basic organizational features of somatosensory representations.

Vibrissal roughness discrimination is barrelcortex-dependent

We have investigated the contribution of the neocortical vibrissal representation within the posterior medial barrel subfield (PMBSF) to the high performance levels obtained by rats in a complex roughness discrimination task mediated by vibrissal inputs. Nine binocularly occluded rats were trained in a two-choice roughness discrimination until they obtained the 85% correct response criteria. Subsequently, the PMBSF was localized by electrophysiological recordings and bilaterally ablated. The locus and extent of the cortical lesions were confirmed by histological analysis after additional training and testing. There was no evidence of task retention after the cortical lesion and barrelless rats were unable to obtain prelesion discriminative performance levels when stimulation was restricted solely to vibrissal cues. After extensive postlesion training, four of these rats were allowed to palpate the discriminanda with their forepaws. Under these conditions rats rapidly reached the 85% correct criterion once again. The present results indicate that the PMBSF is essential for complex tactile discrimination when sensory information is obtained through the vibrissae by active palpation. This deficit is specific for the vibrissal system, the PMBSF is not essential to solve the same tactile discrimination task when the source of the somatosensory information is provided by other non-vibrissal cutaneous sensory receptors.

Method for adaptive training of listening and language comprehension using processed speech within an animated story

A method for adaptively training a subject, using auditory processing of phonemes within command sentences, to improve the subjects listening comprehension, grammatical parsing, and serial memory is provided. The method utilizes a number of training installments, each designed for testing a particular aspect of the subjects language skills, all tied together by a common story. More specifically, installments are provided that narrate a story, test the subjects listening comprehension to the narrated story, test the subjects ability to grammatically parse increasingly difficult sentence structures, and test the subjects ability to select and manipulate graphical objects in response to auditory commands. Speech processing is used for the narration, as well as for commands within each test to allow the subject to more easily distinguish between similar sounding phonemes. As the subject improves his/her ability to correctly respond to the tests, the amount of processing applied to the commands is reduced, ultimately to the level of normal speech.

Speech modifications algorithms used for training language learning-impaired children

In this paper, the details of processing algorithms used in a training program with language learning-impaired children (LLIs) are described. The training program utilized computer games, speech/language training exercises, books-on-tape and educational CD-ROMs. Speech tracks in these materials were processed using these algorithms. During a four week training period, recognition of both processed and normal speech in these children continually increased to near age-appropriate levels. We conclude that this form of processed speech is subject to profound perceptual learning effects and exhibits widespread generalization to normal speech. This form of learning and generalization contributes to the rehabilitation of temporal processing deficits and language comprehension in this subject population.