In the blink of an eye: Real-time stimulus factors in delay and trace conditioning of the rabbit's nictitating membrane response

Since Pavlov, theories of conditioning have assumed that CR evocation is governed by a series of internal stimuli generated by the CS. This hypothesis was tested in conditioning of the rabbit's nictitating membrane (NM) response by attempting to manipulate the internal sequence through truncating a delay CS and extending a trace CS on test trials. These perturbations of CS duration produced large deficits in CR likelihood and smaller alterations in the CR's time course. As predicted by many models of conditioning, the onset of the CS appeared to play a large but not exclusive role compared to CS duration and CS offset in both evocation and timing of the CR. The results are discussed with respect to their implications for real-time models of conditioning.     

Cardiac autonomic reactivity and recovery in predicting carotid atherosclerosis: the cardiovascular risk in young Finns study.

The present study examined the association of cardiac autonomic task-induced reactivity and recovery to preclinical atherosclerosis. Thirty-three men and 33 women aged 24-39 years participated in the ongoing epidemiological Cardiovascular Risk in Young Finns study. The authors measured heart rate (HR), respiratory sinus arrhythmia (RSA), and preejection period (PEP) during the mental arithmetic and speech tasks in 1999. Carotid atherosclerosis was assessed by measuring the thickness of the common carotid artery intima-media complex (IMT) with ultrasound in 2001. Higher HR, RSA, and PEP reactivity were associated with lower IMT values even after adjusting for cardiovascular risk factors (lipid levels, obesity, and blood pressure). In addition, better HR recovery after the mental arithmetic task was associated with lower IMT values, and this association persisted after all adjustments. Thus, higher task-induced cardiac autonomic reactivity and better HR recovery were related to less preclinical atherosclerosis. The authors concluded that cardiac pattern of reactivity and quick recovery may be associated with better cardiovascular health, and therefore all reactivity occurring in challenging situations should not automatically be considered as potentially pathological.