Biomedical subjects

Jessie J Peissig

Publications and source records attributed to Jessie J Peissig.

9 recordsLinked to original sources

PubMed2007

Visual object recognition: do we know more now than we did 20 years ago?

We review the progress made in the field of object recognition over the past two decades. Structural-description models, making their appearance in the early 1980s, inspired a wealth of empirical research. Moving to the 1990s, psychophysical evidence for view-based accounts of recognition challenged some of the fundamental assumptions of structural-description theories. The 1990s also saw increased interest in the neurophysiological study of high-level visual cortex, the results of which provide some constraints on how objects may be represented. By 2000, neuroimaging arose as a viable means for connecting neurons to behavior. One of the most striking fMRI results has been category selectivity, which provided further constraints for models of object recognition. Despite this progress, the field is still faced with the challenge of developing a comprehensive theory that integrates this ever-increasing body of results and explains how we perceive and recognize objects.

Attention↗

PubMed2006

Initial saccades predict manual recognition choices in the monkey.

In animals with specialized foveae, eye position has a direct influence over the acquisition of detailed visual information. At the same time, eye movements executed during natural behaviors are closely linked with motor actions. In this study, we investigated patterns of eye movements during a simple visual discrimination task. Three rhesus monkeys learned to recognize images of real world objects with no explicit constraints on eye position. Analysis of the monkeys' eye movements showed that although the endpoint of the initial saccade depended on the particular visual stimulus, the trajectory of the first saccades also reliably predicted the manual response associated with that stimulus. We thus observed that initial saccades executed in a recognition task reflect both perceptual and motor aspects of a visual task. This pattern of eye movements emerged spontaneously in all three animals tested despite the fact that saccades were never explicitly rewarded. As the average saccade latency was under 200ms, object specific learned associations must have exerted their influence over the initial saccade even earlier, providing a novel temporal marker for the rapidity of visual recognition processes. Taken together, these results suggest that caution should be exercised when interpreting the meaning of oculomotor patterns observed during perceptual tasks, as these blur the line between perceptual processing and motor preparation.

Animals↗

PubMed2006

Effects of long-term object familiarity on event-related potentials in the monkey.

Although some change in the neural representation of an object must occur as it becomes familiar, the nature of this change is not fully understood. In humans, it has been shown that the N170-an evoked visual potential-is enhanced for classes of objects for which people have visual expertise. In this study, we explored whether monkeys show a similar modulation in event-related potential (ERP) amplitude as a result of long-term familiarity by recording ERPs with chronically implanted electrodes over extended training periods spanning many sessions. In each of 3 experiments, we found larger amplitude visual evoked responses to highly familiar images for the time period of 120-250 ms after stimulus onset. This difference was found when the monkeys were trained in an individual-level discrimination task, in a task that required only color discrimination, and even following a viewing-only task. We thus observed this familiarity effect across several tasks and different object categories and further found that the difference between "familiar" and "novel" became smaller as the animals gained experience with the previously unfamiliar objects across multiple test sessions. These data suggest that changes in visual responses associated with familiarity are evident early in the evoked visual response, are robust, and may be automatic, driven at least in part by repeated object exposure.

Animals↗

PubMed2006

XOR style tasks for testing visual object processing in monkeys.

Using visually complex stimuli, three monkeys learned visual exclusive-or (XOR) tasks that required detecting two way visual feature conjunctions. Monkeys with passive exposure to the test images, or prior experience, were quicker to acquire an XOR style task. Training on each pairwise comparison of the stimuli to be used in an XOR task provided nearly complete transfer when stimuli became intermingled in the full XOR task. Task mastery took longer, accuracy was lower, and response times were slower for conjunction stimuli. Rotating features of the XOR stimuli did not adversely effect recognition speed or accuracy.

Animals↗

PubMed2006

Effects of varying stimulus size on object recognition in pigeons.

The authors investigated the pigeon's ability to generalize object discrimination performance to smaller and larger versions of trained objects. In Experiment 1, they taught pigeons with line drawings of multipart objects and later tested the birds with both larger and smaller drawings. The pigeons exhibited significant generalization to new sizes, although they did show systematic performance decrements as the new size deviated from the original. In Experiment 2, the authors tested both linear and exponential size changes of computer-rendered basic shapes to determine which size transformation produced equivalent performance for size increases and decreases. Performance was more consistent with logarithmic than with linear scaling of size. This finding was supported in Experiment 3. Overall, the experiments suggest that the pigeon encodes size as a feature of objects and that the representation of size is most likely logarithmic.

Animals↗

PubMed2005

The role of edges in object recognition by pigeons.

In three experiments, we explored how pigeons use edges, corresponding to orientation and depth discontinuities, in visual recognition tasks. In experiment 1, we compared the pigeon's ability to recognize line drawings of four different geons when trained with shaded images. The birds were trained with either a single view or five different views of each object. Because the five training views had markedly different appearances and locations of shaded surfaces, reflectance edges, etc, the pigeons might have been expected to rely more on the orientation and depth discontinuities that were preserved over rotation and in the line drawings. In neither condition, however, was there any transfer from the rendered images to the outline drawings. In experiment 2, some pigeons were trained with line drawings and shaded images of the same objects associated with the same response (consistent condition), whereas other pigeons were trained with a line drawing and a shaded image of two different objects associated with the same response (inconsistent condition). If the pigeons perceived any correspondence between the stimulus types, then birds in the consistent condition should have learned the discrimination more quickly than birds in the inconsistent condition. But, there was no difference in performance between birds in the consistent and inconsistent conditions. In experiment 3, we explored pigeons' processing of edges by comparing their discrimination of shaded images or line drawings of four objects. Once trained, the pigeons were tested with planar rotations of those objects. The pigeons exhibited different patterns of generalization depending on whether they were trained with line drawings or shaded images. The results of these three experiments suggest that pigeons may place greater importance on surface features indicating materials, such as food or water. Such substances do not have definite boundaries cued by edges which are thought to be central to human recognition.

Animals↗

PubMed2004

The role of surface pigmentation for recognition revealed by contrast reversal in faces and Greebles.

Faces are difficult to recognize when viewed as negatives [Galper (1970). Recognition of faces in photographic negative. Psychonomic Science, 19, 207]. Here we examined the contribution of surface properties to this contrast effect, and whether it is modulated by object category. We tested observers in a matching task using faces or Greebles, presented with or without pigmentation. When stimulus pairs were shown with mismatched contrast (e.g., positive-negative), there was a decrement in performance. This decrement was larger when the stimuli were shown with pigmentation, and this difference was more pronounced with faces than with Greebles. Overall, contrast reversal disrupts the recognition of both faces and objects to a greater degree in the presence of pigmentation, suggesting that surface properties are important components of the object representation.

Color Perception↗

PubMed2002

Learning an object from multiple views enhances its recognition in an orthogonal rotational axis in pigeons.

In the natural environment, most objects are seen from several different viewpoints. We explored the nature of recognition after training with multiple views and compared it to recognition after training with only one view. Pigeons were taught with either five views or one view of each of four single-geon objects. Pigeons trained with five views responded more accurately to novel views of an object than did pigeons trained with only one view. This result held even when the novel views came from a rotational axis that was orthogonal to the training axis. These results do not accord with recognition processes involving mental rotation or direct interpolation. Pigeons trained with five views may have formed a view-invariant representation [Psychol. Rev. 94 (1987) 115; Vision Res. 39 (1999) 2885]; alternatively, they may have acquired a more detailed shape space of the objects in which to measure object similarity [Representation and recognition in vision, MIT Press, MA, 1999], or learned to attend to a broader range of features of each object [J. Exp. Anal. Behav. 54 (1990) 69].

Animals↗

PubMed2002

Brief presentations are sufficient for pigeons to discriminate arrays of same and different stimuli.

Four pigeons first learned to discriminate 16-item arrays of same from different pictorial stimuli. They were then tested with reduced exposure to the pictorial arrays, brought about by changes in the stimulus viewing requirement under fixed-ratio (FR) and fixed-interval (FI) schedules. Increasing the FR requirement enhanced discriminative performance up to 10 pecks; increasing the FI requirement enhanced discriminative performance up to 5 s. Exposures to the stimulus arrays averaging only 2 s supported reliable discrimination. Pigeons thus discriminate same from different stimuli with considerable speed, suggesting that same-different discrimination behavior is of substantial adaptive significance.

Animals↗