Long-term potentiation (LTP) is a candidate synaptic mechanism underlying learning and memory that has been studied extensively at the cellular and molecular level in laboratory animals. To date, LTP has only been directly demonstrated in humans in isolated cortical tissue obtained from patients undergoing surgery, where it displays properties identical to those seen in non-human preparations. Inquiry into the functional significance of LTP has been hindered by the absence of a human model. Here we give the first demonstration that the rapid repetitive presentation of a visual checkerboard (a photic 'tetanus') leads to a persistent enhancement of one of the early components of the visual evoked potential in normal humans. The potentiated response is largest in the hemisphere contralateral to the tetanized visual hemifield and is limited to one component of the visual evoked response (the N1b). The selective potentiation of only the N1b component makes overall brain excitability changes unlikely and suggests that the effect is due instead to an LTP process. While LTP is known to exist in the human brain, the ability to elicit LTP from non-surgical patients will provide a human model system allowing the detailed examination of synaptic plasticity in normal subjects and may have future clinical applications in the assessment of cognitive disorders.

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Matching names and rotated line drawings of objects showed effects of object orientation that depended on name level. Large effects, in the same range as object naming, were found for rotations between 0 degrees and 120 degrees from upright with subordinate names (e.g., collie), whereas nonsignificant effects were found with superordinate (e.g., animal) and basic names (e.g., dog). These results support image normalization, after contact with orientation-invariant representations, that provide basic-level identity. They consequently fail to support theories of object recognition in which rotated object images are normalized to the upright position before contact with long-term object representations.

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Illusory line motion (ILM) refers to the perception of motion in a bar that is presented all at once next to an inducing stimulus. The experimental methods for producing and quantifying ILM are varied, and the resulting explanations are likewise at odds. The current study examined the explanations for ILM away from the inducing stimulus (bright or dark flash) using bars that either suddenly appear (onset bars) or suddenly disappear (offset bars). Real motion is used to cancel ILM, providing three measures to quantify ILM: the consistency of responding to only ILM in the absence of real motion; the distance between the points of subjective equality between ILM and the real motion; and the area between the curves relating perception of motion to the real and illusory conditions. ILM quantities for onset and offset bars are strongly correlated when the bar change occurs after the flash. However, onset bars presented during the flash do not show any evidence of ILM, whereas offset bars removed during the flash result in reverse ILM (rILM). Moreover, rILM and ILM are not correlated, suggesting they reflect two separate illusions. These results are consistent over the various measures of ILM.Keywords Attention . Illusory line motion . Motion perception Forms of illusory line motion (ILM) have been investigated since the early 1900s. There have been a number of paradigms employed, and the phenomenon has been quantified in different ways. As a result, a range of explanations has been offered. This variety, while providing a rich source of data, presents its own problems. Primarily, the lack of consistency in protocols and measurements makes it difficult to know if the results arising from one study are relevant to a study using different methods or measuring different quantities. One cannot be sure they are examining the same underlying phenomena. What follows is not so much an attempt to determine which explanations of illusory line motion are supported or valid and which can be dismissed or rejected, but rather a presentation that attempts to determine what findings warrant a common explanation and what findings can be argued to be reflective of a different illusory phenomenon. After coverage of the literature illustrating the variations of methods, we focused primarily on illusory line motion that occurs following a brief luminance change and made recommendations with respect to experimental methods, quantification of ILM, and data analyses.

Rotated mirror/normal letter discriminations are thought to require mental rotation in order to determine the direction of facing of the stimulus. The response time (RT) function over orientation tends to be curved, rather than the linear function found for other mental rotation tasks. The present study investigated the possibility that the curved RT function is a result of a mixture of trials requiring and not requiring mental rotation. The results suggested that the frequency of mental rotation is also a linear function of stimulus orientation. Moreover, the relationship between an individual's rate of plane rotation and the mean difference in RT between mirror and normal stimuli was replicated, supporting the suggestion that mirrored stimuli are flipped after they are spun (Hamm, Johnson, & Corballis, 2004). On the basis of the present findings, the entire RT function can be modeled by using only the mean RTs for upright and inverted stimuli.