Early Infantile Autism
Children's Neurology Service, Massachusetts General Hospital, Boston 02114, USA. International Review of Neurobiology
(Impact Factor: 1.92).
02/1997; 41:367-86. DOI: 10.1016/S0074-7742(08)60360-8
Autism is a behaviorally defined syndrome. Symptoms become evident by three years of age and include atypical social interaction, disordered language and cognitive skills, impaired imaginary play, poor eye contact, and an obsessive insistence on sameness. Perseveration, repetitive, and stereoptypic behavior and a restricted range of interests may be present in some cases. In physical appearance, a significant number of autistic individuals exhibit hypotonia, dyspraxia, and a disordered modulation of sensory input. Some clinical features of autism have been reported in conditions such as tuberous sclerosis, phenylketonuria, and fragile X syndrome; however in most cases, a specific etiology cannot be identified. With the introduction of magnetic resonance imaging (MRI), morphometric analysis of specific brain structures became the focus of neuroimaging research in autism. These studies have largely concentrated on the cerebellum. Consistent microscopic abnormalities were observed in the brains of nine autistic individuals that were confined to the limbic system and cerebellar circuits. The findings in the cerebellum and related inferior olive suggested that the process, which resulted in these morphologic changes, occurred or had its onset before birth.
Available from: David Mankuta
- "Imaging studies indicate increased brain volume in autistic children between 2 and 4.5 years . The overall brain weight in youngsters with autism is statistically heavier than that of age-and sex-matched controls . A study comparing growth data of children with ASD to those with other psychological disorders confirmed the accelerated head growth in ASD . "
[Show abstract] [Hide abstract]
ABSTRACT: The basic hypothesis for this study is that reduced peripartum level of insulin-like growth factor-1 (IGF) due to genetic, epigenetic, or environmental factors is a sentinel biomarker of increased probability of later development of autism. The central objective of the resultant proposed study described here is examining if a correlation exists between the serum level of IGF in the fetus/newborn and the probability of autism developing later in the child. Mechanisms possibly causing such a decrease are considered. This would define a prospective biomarker for and possible etiology of this disorder. Insulin-like growth factor-1 directly affects the rate at which oligodendrocytes promote myelination in the central nervous system, especially in the brain. Factors which reduce the production or availability of IGF could retard normal nerve programming in the fetus or neonate. Thus, it would be desirable to arrest the pathologic processes of autism in the early neonatal stage before irreversible nerve damage occurs.
Available from: Warren Meck
- "Although a neurobehavioural disorder, its underlying pathophysiology is not well understood. However, 'abnormalities' in the function of the prefrontal cortex, basal ganglia and cerebellum have been heavily implicated (Bauman et al., 1997; Sears et al., 1999; Allen et al., 2004; Hollander et al, 2005; Haznedar et al, 2006; Voelbel et al., 2006) as have a variety of neurotransmitters, including dopamine and serotonin (Makkonen et al., 2008; Nakamura et al., 2010)—both of which have been implicated in timing and time perception (Coull et al., 2008, 2011; Sysoeva et al., 2010; Meck et al., 2011; Weiner et al., 2011). Allman et al. (2011a) "
[Show abstract] [Hide abstract]
ABSTRACT: Distortions in time perception and timed performance are presented by a number of different neurological and psychiatric conditions (e.g. Parkinson's disease, schizophrenia, attention deficit hyperactivity disorder and autism). As a consequence, the primary focus of this review is on factors that define or produce systematic changes in the attention, clock, memory and decision stages of temporal processing as originally defined by Scalar Expectancy Theory. These findings are used to evaluate the Striatal Beat Frequency Theory, which is a neurobiological model of interval timing based upon the coincidence detection of oscillatory processes in corticostriatal circuits that can be mapped onto the stages of information processing proposed by Scalar Timing Theory.
Available from: Lauren Kenworthy
- "However, this effect appears to be age-dependent, as the most pronounced period of head/brain enlargement occurs in early postnatal periods, perhaps ages 1–4 years (Courchesne et al., 2001; Hazlett et al., 2005; Schumann et al., 2010), while this atypical enlargement is increasingly absent later in development. For example, while post-mortem brain weights for children with autism spectrum disorders are generally comparable with those of same age controls, adults with autism spectrum disorders tend to have lighter post-mortem brains than adult controls (Bauman and Kemper, 1997). Furthermore, Aylward and colleagues (2002) found that children with autism spectrum disorders of 8–12 years of age had larger brain volumes than their same-age typically developing peers, while typically developing individuals and those with autism spectrum disorders ranging in age from 12 to 46 years had comparable brain volumes. "
[Show abstract] [Hide abstract]
ABSTRACT: Studies of head size and brain volume in autism spectrum disorders have suggested that early cortical overgrowth may be followed by prematurely arrested growth. However, the few investigations quantifying cortical thickness have yielded inconsistent results, probably due to variable ages and/or small sample sizes. We assessed differences in cortical thickness between high-functioning adolescent and young adult males with autism spectrum disorders (n = 41) and matched typically developing males (n = 40). We hypothesized thinner cortex, particularly in frontal, parietal and temporal regions, for individuals with autism spectrum disorders in comparison with typically developing controls. Furthermore, we expected to find an age × diagnosis interaction: with increasing age, more pronounced cortical thinning would be observed in autism spectrum disorders than typically developing participants. T(1)-weighted magnetization prepared rapid gradient echo 3 T magnetic resonance imaging scans were acquired from high-functioning males with autism spectrum disorders and from typically developing males matched group-wise on age (range 12-24 years), intelligence quotient (≥ 85) and handedness. Both gyral-level and vertex-based analyses revealed significantly thinner cortex in the autism spectrum disorders group that was located predominantly in left temporal and parietal regions (i.e. the superior temporal sulcus, inferior temporal, postcentral/superior parietal and supramarginal gyri). These findings remained largely unchanged after controlling for intelligence quotient and after accounting for psychotropic medication usage and comorbid psychopathology. Furthermore, a significant age × diagnosis interaction was found in the left fusiform/inferior temporal cortex: participants with autism spectrum disorders had thinner cortex in this region with increasing age to a greater degree than did typically developing participants. Follow-up within group comparisons revealed significant age-related thinning in the autism spectrum disorders group but not in the typically developing group. Both thinner temporal and parietal cortices during adolescence and young adulthood and discrepantly accelerated age-related cortical thinning in autism spectrum disorders suggest that a second period of abnormal cortical growth (i.e. greater thinning) may be characteristic of these disorders.
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.