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There are suggestions in the literature that spatial precuing of attention with peripheral and central cues may be mediated by different mechanisms. To investigate this issue, data from two previous papers were reanalysed to investigate the complete time course of precuing target location with either: (1) a peripheral cue that may draw attention reflexively, or (2) a central, symbolic cue that may require attention to be directed voluntarily. This analysis led to predictions that were tested in another experiment. The main result of this experiment was that a peripheral cue produced its largest effects on discrimination performance within 100 msec, whereas a central cue required approximately 300 msec to achieve maximum effects. In conjunction with previous findings, the present evidence for time differences between the two cuing conditions suggests that more than one process is involved in the spatial precuing of attention.

The gross morphology of the tongue of the Mongolian gerbil Meriones unguiculutus), the location of papillae and taste buds, and the normal innervation pattern of the tongue and taste buds were determined. The chorda tympani nerve was interrupted to produce degeneration of fungiform taste buds. Regenerating chorda tympani axons followed the original nerve pathways in the tongue en route to the fungiform papillae in the epithelium where they initiated the regeneration of taste buds. The spatial distribution of reinnervated fungiform papillae and reformed taste buds was examined 7 to 19 days following surgery.Beginning at eight days following chorda tympani interruption there was a progressive increase, first, in the proportion of fungiform papillae that were reinnervated, and later in the number of reformed taste buds. On the basis of these measures it was concluded that a taste bud is reformed one to two days after reinnervation of its papilla. From the time course of reinnervation of the fungiform papillae it was calculated that some fibers regenerated at rates in excess of 2 mm/day. Regeneration was precise and systematic. The regenerating chorda tympani fibers accurately returned to the fungiform papillae; they did not follow the pathways of lingual nerve axons. In the initial stages of recovery both reinnervated papillae and reformed taste buds were preferentially located toward the front of the tongue; the reinnervation of posterior fungiform papillae was delayed.

Precuing a location facilitates accuracy of identification of a target at that location and reduces noise from other nontarget characters in a multicharacter field. In 5 experiments, evidence for facilitation included higher accuracy with long precue-target intervals than with short intervals and higher accuracy when a precue indicated the correct location than with short intervals and higher accuracy when a precue indicated the correct location than when it indicated the wrong location. These results were found for each target-mask condition used (1 target with 1 mask, 1 target with 4 masks, or 1 target and 3 nontargets with 4 masks) in experienced and inexperienced observers. Evidence for noise reduction was found because accuracy was higher in the 1 target-1 mask condition than in the other conditions on correctly cued trials with short-cue-target intervals and on incorrectly cued trials. Data are related to methodological factors that are important to obtaining these effects and to capacity and noise reduction models.

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