Visual Paired Comparison Task Research Articles

Impaired Recognition Memory in Rats after Damage to the Hippocampus

Rats with radio-frequency or ibotenic acid lesions of the hippocampus and rats with radio-frequency lesions of the fornix were tested on the visual paired comparison task (VPC), a test of recognition memory. Memory was assessed at five different delay intervals ranging from 10 sec to 24 hr. All operated groups performed normally at the shorter delays (10 sec and 1 min). Across longer delays, the two groups with hippocampal damage were impaired. Rats with fornix lesions performed well on the VPC task but were impaired on a spatial task (spontaneous alternation). The results show that the hippocampus is essential for normal recognition memory. Moreover, fornix lesions need not mimic the effects of direct damage to hippocampal tissue. The findings are discussed in the context of the contribution of the hippocampus to recognition memory.

Visual Recognition Memory for Objects in Six- and Nine-Month-Old Infants

Developmental trends in recognition memory were examined in typically-developing 6- and 9-month-old infants using the Visual Paired-Comparison task (VPC). The VPC exploits an infant's natural tendency to look longer at a novel stimulus than at a familiar one with which it has been paired. The results show that infants of both ages display a novelty preference (i.e., recognition memory) when the delay interval is 10 seconds or 5 minutes in duration. However, after a delay of 1 week, 6-month-old infants are performing at chance levels of responding while 9-month-old infants tend to look longer at the familiar stimulus. The possibility that the younger infants' performance reflects forgetting while the older infants are updating memory is discussed. The importance of assessing infant recognition memory is discussed in light of recent findings that this measure has predictive reliability for cognitive function in later childhood.

Impaired Recognition Memory in Monkeys after Damage Limited to the Hippocampal Region

Monkeys with lesions limited to the hippocampal region (the hippocampus proper, the dentate gyrus, and the subiculum) were impaired on two tasks of recognition memory: delayed nonmatching to sample and the visual paired-comparison task. Recognition memory was impaired in five different groups of monkeys, whether the lesions were made by an ischemic procedure, by radio frequency, or by ibotenic acid. The finding that the hippocampal region is essential for normal recognition memory performance is considered in the context of current ideas about the role of the hippocampus in declarative memory.

Dissociation between the effects of damage to perirhinal cortex and area TE.

Perirhinal cortex and area TE are immediately adjacent to each other in the temporal lobe and reciprocally interconnected. These areas are thought to lie at the interface between visual perception and visual memory, but it has been unclear what their separate contributions might be. In three experiments, monkeys with bilateral lesions of the perirhinal cortex exhibited a different pattern of impairment than monkeys with bilateral lesions of area TE. In experiment 1, lesions of the perirhinal cortex produced a multimodal deficit in recognition memory (delayed nonmatching to sample), whereas lesions of area TE impaired performance only in the visual modality. In experiment 2, on a test of visual recognition memory (the visual paired comparison task) lesions of the perirhinal cortex impaired performance at long delays but spared performance at a very short delay. In contrast, lesions of area TE impaired performance even at the short delay. In experiment 3, lesions of the perirhinal cortex and lesions of area TE produced an opposite pattern of impairment on two visual discrimination tasks, simple object discrimination learning (impaired only by perirhinal lesions), and concurrent discrimination learning (impaired only by TE lesions). Taken together, the findings suggest that the perirhinal cortex, like other medial temporal lobe structures, is important for the formation of memory, whereas area TE is important for visual perceptual processing.

Neonatal aspiration lesions of the hippocampal formation impair visual recognition memory when assessed by paired-comparison task but not by delayed nonmatching-to-sample task.

Previous experiments showed that neonatal aspiration lesions of the hippocampal formation in monkeys yield no visual recognition loss at delays up to 10 min, when recognition memory was assessed by a trial-unique delayed nonmatching-to-sample (DNMS) task. The present study examined whether neonatal hippocampal lesions also have no effect on visual recognition when assessed by a visual paired-comparison (VPC) task. In the VPC task, animals are looking at visual stimuli and their preference for viewing new stimuli is measured. Normal adult monkeys showed strong preference for looking at the novel stimuli at all delays tested. By contrast, adult monkeys with neonatal hippocampal lesions, which included the dentate gyrus, cornus ammon (CA) fields, subicular complex, and portions of parahippocampal areas TH/TF, showed preference for novelty at short delays of 10 s but not at longer delays of 30 s to 24 h. This visual recognition loss contrasts with the normal performance of the same operated animals when tested in the DNMS task. The discrepancy between the results obtained in the two recognition tasks suggests that, to perform normally on the DNMS task, the operated monkeys may have used behavioral strategies that do not depend on the integrity of the hippocampal formation. In this respect, VPC appears to be a more sensitive task than DNMS to detect damage to the hippocampal region in primates.

Face recognition in primates: a cross-species study

Recognition for human faces, monkey faces, and objects was assessed in both adult humans ( Homo sapiens) and monkeys ( Macaca mulatta) with a visual paired-comparison task. The results demonstrated that while both species showed strong novelty preference for objects, human participants showed novelty preference for human faces but not for monkey faces, and vice versa for the monkeys. This `species-specific effect' in face recognition is discussed in relation with data on both the `other-race effect' observed in humans and the effects of experience or training on face recognition processes in primates.

Long-term recognition memory for faces assessed by visual paired comparison in 3- and 6-month-old infants.

It has been argued that operant conditioning is the only type of long-term memory present in infants prior to 6 months of age. In this study, memory for faces was investigated in 3- and 6-month-old infants with a visual paired-comparison task. In Experiment 1, infants were habituated to a face presented in different poses; recognition was assessed after a 2-min or a 24-hr retention interval. The 6-month-old infants and the male but not (he female 3-month-old infants exhibited novelty preferences. A 2nd experiment showed that 3-month-old female infants were delayed relative to male infants in their face-processing ability rather than in their memory capacity. The results of Experiment 3 demonstrated in 3-month-olds an electrophysiological correlate of delayed recognition memory. These findings are discussed in the context of the neural systems thought to be involved in visual recognition memory (but not in procedural memory), namely the limbic system. One crucial issue in developmental psychology is to understand when and how episodes taking place in infants' environments modify their cortical representations of the world and their expertise in various cognitive abilities. For several years, researchers have essentially attempted to describe the cognitive abilities that may guide learning and memory at the very beginning of life. Investigations of memory itself in this same early period of life were scarce. For instance, there are numerous studies of the development of face processing in infancy (for a review, see de BoyssonBardies, de Schonen, Jusczyk, MacNeilage, & Morton, 1993). In contrast, there are almost no data available on memory for faces. Thus, it remains unclear when infants become able to memorize exemplars of several different faces, for how long they can retain these memories, how far memory for exemplars is involved in the early development of face-processing competencies, and whether the develomental path for face memory is the same as for object memory. To model the development of cortical functions and cogni

Long-term recognition memory for faces assessed by visual paired comparison in 3- and 6-month-old infants.

It has been argued that operant conditioning is the only type of long-term memory present in infants prior to 6 months of age. In this study, memory for faces was investigated in 3- and 6-month-old infants with a visual paired-comparison task. In Experiment 1, infants were habituated to a face presented in different poses; recognition was assessed after a 2-min or a 24-hr retention interval. The 6-month-old infants and the male but not the female 3-month-old infants exhibited novelty preferences. A 2nd experiment showed that 3-month-old female infants were delayed relative to male infants in their face-processing ability rather than in their memory capacity. The results of Experiment 3 demonstrated in 3-month-olds an electrophysiological correlate of delayed recognition memory. These findings are discussed in the context of the neural systems thought to be involved in visual recognition memory (but not in procedural memory), namely the limbic system.

Evidence of Robust Recognition Memory Early in Life Even When Assessed by Reaching Behavior

Infants of only 5-6 months prefer to look at something new when given the choice of looking at a stimulus shown earlier or something new, even after a long delay (the visual paired comparison task). However, if infants must reach and displace a stimulus to retrieve a reward, even 18-month-olds respond randomly when given the choice of reaching to the stimulus shown earlier or to something new, even after a brief delay (the delayed nonmatching to sample task). To investigate this paradox we modified the delayed nonmatching to sample task to make it more similar to visual paired comparison. Each stimulus served as its own reward; no rewards were hidden under any stimuli. Infants were habituated to a sample object, a delay was imposed, and then the sample and a new object were presented. Infants could choose to look at (in visual paired comparison) or reach for (in delayed nonmatching to sample (stimulus = reward)) either object. One hundred twenty infants were tested: 60 (20 each at 4, 6 and 9 months) on visual paired comparison and 60 (20 each at 6, 9 and 12 months) on delayed nonmatching to sample (stimulus = reward). The same 10 pairs of stimuli were used on both tasks. Each subject was tested twice at all five delays (10, 15, 60, 180 and 600 s). At even the youngest age that reaching was tested (6 months), infants showed evidence of recognition memory on the reaching task at delays at least as long as those at which they demonstrated recognition memory on the looking task. Indeed, when subjects reached, not in order to obtain something else, but to obtain the stimulus itself, they succeeded on a recognition memory task even at delays 10 min long very early in life.

On the development of declarative memory.

In the visual paired-comparison task, which has been used to demonstrate memory abilities in human infants, Ss view pairs of pictures and then view new pictures paired with old ones. Memory is demonstrated when Ss spend more time looking at new pictures than at old ones. In a series of studies involving amnesic patients and normal Ss, the authors evaluated what kind of memory is exhibited in this task. The results suggest that performance ordinarily depends on the brain structures essential for declarative memory. These and other findings suggest that the visual paired-comparison test also depends on declarative memory when the task is given to human infants. Thus, successful performance on this task by infants probably reflects an early capacity for declarative memory. The relevance of these findings to the phenomenon of infantile amnesia is discussed.

Ontogenetic Development of Habit and Memory Formation in Primates

Lesion studies in adult monkeys have suggested that an experience can enter into memory in two ways: as cognitive information stored in a cortico-limbo-thalamocortical system (involving the higher order sensory areas of cortex, the amygdala, hippocampus, and entorhinal cortex, the medial thalamic nuclei, or ventromedial prefrontal cortex, and the basal forebrain) and as a habit stored perhaps in a cortico-striatal system (involving the sensory cortical areas and the caudate and putamen). Our studies of behavioral development in infant monkeys as well as those in human infants provide complementary evidence by suggesting that these two systems are developmentally dissociable, in that the cognitive memory system, assessed by the delayed non-matching to sample task, appears to mature considerably more slowly than the habit system, assessed by the concurrent visual discrimination task, a notion that has also been discussed recently by others (Nadel & Zola-Morgan, 1984; Rose, 1980). Furthermore, despite the late development of the cortico-limbo-diencephalic memory system, this chapter has presented evidence that some limbic-dependent memory processes, such as those required for success on the visual paired comparison task, develop extremely early. The notion that at least one type of recognition process mediated by the limbic system is present neonatally provides new insight into the normal development of memory processes and indicates the need to identify further the memory processes and substrates that become available to an infant at different time points during maturation. Such studies will help one day to determine the immaturity of structure or function that is responsible for the intriguing phenomenon of infantile amnesia, that is, the inability to recall the stimuli or events experienced in the first few years of life.