So it is with the dreams whose first impulse is some central or spontaneous excitation.

A momentary sight of a face or even the mention of a name during the preceding day may give the start to dream-activity; but all subsequent members of the series of images owe their revival to a tension, so to speak, in the fine threads which bind together, in so complicated a way, our impressions and ideas.
Among the psychic accompaniments of these central excitations visual images, as already hinted, fill the most conspicuous place.

Even auditory images, though by no means absent, are much less numerous than visual.

Indeed, when there are the conditions for the former, it sometimes happens that the auditory effect transforms itself into a visual effect.

An illustration of this occurred in my own experience.
Trying to fall asleep by means of the well-known device of counting, I suddenly found myself losing my hold on the faint auditory effects, my imagination transforming them into a visual spectacle, under the form of a path of light stretching away from me, in which the numbers appeared under the grotesque form of visible objects, tumbling along in glorious confusion.
Next to these visual phantasms, certain motor hallucinations seem to be most prominent in dreams.