Cognition distributed

D.E. Rumelhart, G.E. Hinton and R.J. Williams, Learning internal representations by error propagation. In Parallel Distributing Processing, Explorations in the Microstructure of Cognition, Vol. 1 Foundations, D.E. Rumelhart and J.L. McClelland (eds.), MIT Press, Cambridge, MA, 1986, pp. 318-362. 

Children appear to be much more sensitive to lead-related neurobehavioral alterations than adults. Neurobehavioral dysfunction has not been demonstrated in lead-exposed workers at PbB concentrations below 40 pg/dL, whereas cognitive and sensorimotor deficits have been shown in children to be associated with PbB concentrations as low as 10 to 15 pg/dL. To put these findings in perspective, a 1-3 point IQ decrement corresponds to 1/5 or less of a standard deviation of the typical IQ distribution. 

In addressing the question of how income inequality is linked to population health, Muntaner and Lynch (1999) identified two strands of causation, thus combining the approaches of Kaplan and Wilkinson. First, they claim that income inequality is associated with a set of social processes and economic policies that systematically under-invest in physical and social infrastructure (e.g. education). Secondly, large disparities in income distribution may have direct consequences on people s perceptions of their relative place in the social environment, which leads to behavioral and cognitive states that influence health. 

Nicotinic receptors are widely distributed in the brain and are involved in a number of physiological processes. The prefrontal cortex is a major site for the cognitive effects of nicotine (Vidal 1996). Some of the cognitive benefits of nicotine may occur after chronic treatment, resulting in part from nicotinic receptor up-regulation in frontal, entorhinal, and dorsal hippocampal regions (Abdulla et al. 1996). Chronic nicotine treatment also increases the sensitivity of muscarinic receptors (Wang et al. 1996). 

Limited data are available on the pharmacokinetics of arecoline. Intravenously administered arecoline in subjects with Alzheimer s disease shows variation in the optimal dose (between 4 and 16 mg/day) due to differing plasma kinetics (Asthana et al. 1996). The mean plasma half-lives for these doses were 0.95 0.54 and 9.3 4.5 minutes, respectively. However, the mean plasma concentrations that optimized cognitive effects were 0.31 0.14 ng/ml. Drug clearance was 13.6 5.8 L/min and the volume of distribution was 205 170 L. 

The consequences of being on the receiving end of an enemy attack with EA 3167 could be severe. Multiple low dose attacks over a period of several days could produce an insidious build-up of cognitive defects. Distributed attacks would also tend to result in a more homogeneous distribution of dosage, since members of the population would probably change their locations at various times and total exposure would thus tend to be more uniform. 

In the elderly, preexisting organic mental disorders, a decreased volume of distribution, and the concurrent use of other medication may potentiate the effects of alcohol on cognition, affect, and behavior (see The Elderly Patient earlier in this chapter). 

Malina et al. (5) have published a constructivist analysis of how instrument use affects student concept development. The goal was to identify those characteristics that were the most important influences on student construction of scientific understanding. They focused on CCD Spectroscopy, and based their work on multiple theoretical frameworks, including distributed cognition and the theory of affordances. 

D. E. Rumelhart and J. L. McClelland, Parallel Distributed Processing Exploration in the Microstructure of Cognition, MIT Press, Cambridge, MA, 1986. 

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