Amplitude of low frequency fluctuations during resting state fMRI in autistic children

Resting state fMRI (rs-fMRI) provides an excellent platform for examining the amplitude of low frequency fluctuations (ALFF) and fractional amplitude of low frequency fluctuations (fALFF), which are key indices of brain functioning. However, ALFF and fALFF have been used only sporadically to study autism. rs-fMRI data from 69 children (40 autistic, mean age = 8.47 ± 2.20 years; age range: 5.2 to 13.2; and 29 non-autistic, mean age = 9.02 ± 1.97 years; age range 5.9 to 12.9) were obtained from the Autism Brain Imaging Data Exchange (ABIDE II). ALFF and fALFF were measured using CONN connectivity toolbox and SPM12, at whole-brain & network-levels. A two-sampled t-test and a 2 Group (autistic, non-autistic) × 7 Networks ANOVA were conducted to test group differences in ALFF and fALFF. The whole-brain analysis identified significantly reduced ALFF values for autistic participants in left parietal opercular cortex, precuneus, and right insula. At the network level, there was a significant effect of diagnostic group and brain network on ALFF values, and only significant effect of network, not group, on fALFF values. Regression analyses indicated a significant effect of age on ALFF values of certain networks in autistic participants. Such intrinsically different network-level responses in autistic participants may have implications for task-level recruitment and synchronization of brain areas, which may in turn impact optimal cognitive functioning. Moreover, differences in low frequency fluctuations of key networks, such as the DMN and SN, may underlie alterations in brain responses in autism that are frequently reported in the literature.

Event related potential exploration of the organizational structure of abstract versus concrete words in neurologically intact younger adults

The purpose of this study was to test the effects of concreteness and relationship type (similarity vs. association) on semantic processing using event-related potentials (ERP). Neurophysiological evidence has been found for the concreteness effect and for an effect of relationship type. This study replicated and extended these findings by investigating the interaction of concreteness and relationship type. Twenty-four neurologically healthy young adults performed lexical decision and semantic relatedness tasks while continuous scalp EEG was recorded. Larger N400 effects were found for concrete words in associative relationships than for concrete words in similarity relationships and abstract words in either type of relationship. The results are discussed in relation to the different representational frameworks account for abstract and concrete word processing.

Behavioral and neurobiological evidence for the effects of reading interventions on autistic children: A systematic review

This study systematically reviewed the literature on reading interventions for autistic children. Peer-reviewed articles that reported behavioral and/or neurobiological effects of reading intervention were identified in five online databases. After screening, 15 studies met the inclusion criteria for this review. These studies focus on interventions targeted towards improving specific reading skills: comprehension, vocabulary, fluency, and phonological awareness. Studied interventions included interactive and shared reading, visualization strategies, vocabulary and main idea instruction, video modeling, and interventions supported by tablet-based technology. Overall, the studies identified in this review reported improvements to each of the targeted reading skills and changes to neural activation and connectivity. In addition, changes at the brain level were associated with improvements in reading. Specifically, frontal, temporal, and occipital regions associated with visual and language processing showed increased activation and functional connectivity following intervention. This review provides important insights into the landscape of reading intervention studies in autism and into the neurobiological underpinnings of reading skills and how interventions affect those processes.

Centering the family in their system: a framework to promote family-centered AAC services

Families are the most significant communication partners for an individual with complex communication needs. Even though family-centered approaches are recommended to support augmentative and alternative communication (AAC) services for an individual, it is difficult to establish a successful plan that fits each individual's family. A framework for practitioners is proposed to effectively obtain and understand information about a family's unique dynamics as part of service delivery to positively impact AAC device uptake and long-term use. The goal of using this model is to minimize the disruption to the family while maximizing the integration of the AAC system. This paper proposes and illustrates a framework to enrich AAC services through the integration of several theoretical models of family systems theory, family paradigms, and a procedure called the self-created genogram. This paper begins by reviewing ecological family systems theory and family systems to guide and provide a framework to support effective AAC implementation. The process of self-creating genograms is then introduced as a means to obtain a rich perspective on family characteristics and dynamics that is informed by the individual who uses AAC. All of this information allows professionals to provide relevant information and tailor options for the family. As a result, the family is able to make informed decisions about AAC intervention in a manner most consistent with how they typically operate. Finally, we apply this framework to a hypothetical case of a child with autism and complex communication needs across three timepoints (preschool, late elementary/early middle school, and high school/post-secondary transition) to demonstrate how this framework can be used in clinical practice.

Brief Report: Visuospatial and Spoken Language Recall in Autism: Preliminary Findings

Challenges to verbal encoding may affect the ability of autistic individuals to express their ideas. Therefore, visuospatial expression may represent a person's knowledge and skills more accurately than spoken language. To test this hypothesis, we asked seven autistic adults to linguistically retell and visuospatially reenact several animated clips. On average, visuospatial responses contained more correct elements than spoken responses. The level of intention of the three stimulus categories did not systematically affect response accuracy. Participants who produced visuospatial responses before spoken responses and those who had watched a greater number of stimuli assigned higher intentionality to shapes in the animations that were designed to elicit mentalizing. The modality used for expression may affect accuracy of responses by autistic individuals.

Development of Neural Structure and Function in Autism Spectrum Disorder: Potential Implications for Learning Language

Purpose Neurodevelopmental processes that begin during gestation and continue throughout childhood typically support language development. Understanding these processes can help us to understand the disruptions to language that occur in neurodevelopmental conditions, such as autism spectrum disorder (ASD). Method For this tutorial, we conducted a focused literature review on typical postnatal brain development and structural and functional magnetic resonance imaging, diffusion tensor imaging, magnetoencephalography, and electroencephalography studies of the neurodevelopmental differences that occur in ASD. We then integrated this knowledge with the literature on evidence-based speech-language intervention practices for autistic children. Results In ASD, structural differences include altered patterns of cortical growth and myelination. Functional differences occur at all brain levels, from lateralization of cortical functions to the rhythmic activations of single neurons. Neuronal oscillations, in particular, could help explain disrupted language development by elucidating the timing differences that contribute to altered functional connectivity, complex information processing, and speech parsing. Findings related to implicit statistical learning, explicit task learning, multisensory integration, and reinforcement in ASD are also discussed. Conclusions Consideration of the neural differences in autistic children provides additional scientific support for current recommended language intervention practices. Recommendations consistent with these neurological findings include the use of short, simple utterances; repetition of syntactic structures using varied vocabulary; pause time; visual supports; and individualized sensory modifications.

Effects of aerobic exercise and gender on visual and auditory P300, reaction time, and accuracy

Visual and auditory reaction times (RTs) have been reported to decrease during moderate aerobic exercise, and this has been interpreted as reflecting an exercise-induced activation (EIA) of cognitive information processing. In the present study we examined changes in several independent measures of information processing (RT, accuracy, P300 latency and amplitude) during exercise, and their relationship to visual or auditory modalities and to gender. P300 latencies offer independent measures of cognitive speed that are unrelated to motor output, and P300 amplitudes have been used as measures of attentional allocation. Twenty-four healthy college students [mean (SD) age 20 (2) years] performed auditory and visual "oddball" tasks during resting baseline, aerobic exercise, and recovery periods. Consistent with previous studies, both visual and auditory RTs during exercise were significantly shortened compared to control and recovery periods (which did not differ from each other). We now report that, paralleling the RT changes, auditory and visual P300 latencies decreased during exercise, indicating the occurrence of faster cognitive information processing in both sensory modalities. However, both auditory and visual P300 amplitudes decreased during exercise, suggesting diminished attentional resource allocation. In addition, error rates increased during exercise. Taken together, these results suggest that the enhancement of cognitive information processing speed during moderate aerobic exercise, although operating across genders and sensory modalities, is not a global facilitation of cognition, but is accompanied by decreased attention and increased errors.

Concurrent visual task effects on evoked and emitted auditory p300 in adolescents

Using an oddball stimulus presentation paradigm, the effects of divided attention on auditory P300s were studied. Auditory attention was either divided or focused, depending on the demands placed on subjects during the performance of a concomitantly presented visual task. Two types of auditory tasks were performed under each of the two auditory attention conditions. In one, subjects responded to infrequently presented high pitched tones (oddball stimuli). In the other they responded to the occasional omission of a stimulus in an otherwise rhythmically presented chain of stimuli. P300s and reaction times were recorded to both the rare tones and the omissions. The Sternberg visual memory task was used to manipulate the subject's auditory attention state. Subjects actively performed the Sternberg task during the divided auditory attention condition, whereas during the focused attention condition they were not required to respond to the visual stimuli. During focused auditory attention, evoked auditory P300s were both larger and faster than their emitted counterparts. During divided attention, auditory P300s were reduced in amplitude but latency was unaffected. Evoked auditory P300s showed evidence of containing P300a as well as P300b components, particularly when attention was shared with the visual task.

P300 delay and attenuation in schizophrenia: reversal by neuroleptic medication

BACKGROUND

P300 amplitude reduction in schizophrenia has been found by many investigators, but P300 latency generally has been reported to be normal; however, conflicting findings are present in the literature, and interpretation has been confounded by medication effects and methodological differences.

METHODS

This study used a standard auditory oddball paradigm to compare the latency, amplitude, and topographic distribution of P300s in neuroleptic-free schizophrenic patients with those of healthy controls. The patients then were treated for 6 weeks with either remoxipride or haloperidol, and their P300s were reassessed.

RESULTS

P300s were attenuated and delayed among neuroleptic-free patients. There was no evidence of peak lateralization or amplitude asymmetry over temporal areas. Subsequent neuroleptic medication normalized P300 latencies and increased P300 amplitudes, but the latter remained below normal limits over all except frontal areas. There were no correlations between P300 latency or amplitude and clinical symptomatology either before or after treatment.

CONCLUSIONS

The finding of a P300 delay in neuroleptic-free schizophrenics that is normalized by neuroleptic medication has not been reported previously. Neuroleptic effects on P300 amplitude and latency appear to be independent of effects on clinical symptoms, and cannot be attributed to anticholinergic activity.

P2 flash visual evoked response delay may be a marker of cognitive dysfunction in healthy elderly volunteers

In an earlier study, 31 healthy elderly volunteers had normal cognitive function as measured by the Mini-Mental State Examination. Twenty-seven returned for further memory testing using the Wechsler Memory Scale-Revised (WMS-R). The P2 latency of the flash visual evoked response was positively correlated with age (p = .0008), but was not significantly related to gender. Nine of these 27 putatively healthy subjects had a delayed P2, suggestive of dementia. Although unaware of any memory deficits, 5 of the 27 had WMS-R Visual Memory Span percentile scores 1 or more standard deviations less than age-matched controls. Four of the five also had a significantly delayed P2 component. This positive correlation, adjusted for age, between poor Visual Memory Span performance and a delayed P2 was statistically significant (p < .025). These findings suggest that a delayed P2 in putatively healthy subjects is indicative of a visuospatial deficit which might be a precursor of dementia later.

Flash P2 delay in primary degenerative dementia of the Alzheimer type

1. Flash visual evoked responses of 31 patients meeting DSM-III-R criteria for primary degenerative dementia of the Alzheimer type were compared with 31 healthy controls. 2. P1 latency was normal (75 +/- 6 msec Alzheimer's; 75 +/- 6 msec controls). 3. P2 was significantly delayed (162 +/- 32 msec, 147 +/- 20 msec, p < 0.03) among patients. 4. P1-P2 interpeak latency was significantly increased (87 +/- 32 msec, 71 +/- 21 msec, p < 0.03) among patients.

EEG-based, neural-net predictive classification of Alzheimer's disease versus control subjects is augmented by non-linear EEG measures

Attempts to classify Alzheimer's disease (AD) subjects versus controls using spectral-band measures of electroencephalographic (EEG) data typically achieve around 80% success. This study assessed the ability of adding non-linear EEG measures and using a neural-net classification procedure to improve this performance level. The non-linear EEG measures were estimated correlation dimension ("dimensional complexity," or DCx) and saturation (degree of leveling-off of DCx with increasing embedding dimension). In a sample of 39 subjects (14 ADs, 25 controls), it was found that (a) the addition of non-linear EEG measures improved the classification accuracy of the AD/control status of subjects, and (b) a back-percolation neural net predictively classified the subjects much better than the standard linear techniques of multivariate discriminant analysis or nearest-neighbor discriminant analysis.

Delayed late component of visual global field power in probable Alzheimer's disease

A substantial literature shows that late components of visual evoked potentials (VEPs) are delayed in at least some forms of dementia in the elderly. The late-component delay is selective in that earlier components are not affected. More recent work with better defined clinical groups suggests that the selective late-component delay may be characteristic of Alzheimer's disease (AD) rather than an inevitable feature of dementia in general. To overcome problems in traditional VEP component latency measurement the present study uses reference-free Global Field Power (GFP) analysis to more objectively define VEP components and finds that the GFP peak corresponding to the late P2 component of the flash VEP is delayed in a probable AD group but not in a demented unlikely AD group, relative to age-equivalent healthy controls. The late-component delay is again found to be selective in that the GFP peak corresponding to the earlier P1 component of the flash VEP does not differ between groups. These findings further strengthen the evidence for electrocortical changes in the visual system of AD patients.

Parallel distributed processing and neuropsychology: a neural network model of Wisconsin Card Sorting and verbal fluency

Neural networks can be used as a tool in the explanation of neuropsychological data. Using the Hebbian Learning Rule and other such principles as competition and modifiable interlevel feedback, researchers have successfully modeled a widely used neuropsychological test, the Wisconsin Card Sorting Test. One of these models is reviewed here and extended to a qualitative analysis of how verbal fluency might be modeled, which demonstrates the importance of accounting for the attentional components of both tests. Difficulties remain in programming sequential cognitive processes within a parallel distributed processing (PDP) framework and integrating exceedingly complex neuropsychological tests such as Proverbs. PDP neural network methodology offers neuropsychologists co-validation procedures within narrowly defined areas of reliability and validity.

HIV and the brain: evidence of early involvement and progressive damage

AIDS is often accompanied by progressive encephalopathy and 'subcortical' dementia, but there is uncertainty regarding how early the brain involvement may begin in the course of HIV infection. This study used a cognitive auditory 'oddball' paradigm to elicit sensory and cognitive event related potential (ERP) components from healthy controls and from patients at different stages of HIV infection. Sensory component latencies did not differ between groups, but cognitive components showed progressive delays corresponding to increasingly severe clinical stages of HIV infection. The earliest changes were found among asymptomatic HIV + patients, suggesting that this test is a sensitive indicator of early subclinical CNS damage. In contrast, neither frequency analysis nor nonlinear dynamical analysis of the EEG showed differences between healthy controls and patients.

Parallel distributed processing and neural networks: origins, methodology and cognitive functions

Parallel Distributed Processing (PDP), a computational methodology with origins in Associationism, is used to provide empirical information regarding neurobiological systems. Recently, supercomputers have enabled neuroscientists to model brain behavior-relationships. An overview of supercomputer architecture demonstrates the advantages of parallel over serial processing. Histological data provide physical evidence of the parallel distributed nature of certain aspects of the human brain, as do corresponding computer simulations. Whereas sensory networks follow more sequential neural network pathways, in vivo brain imaging studies of attention and rudimentary language tasks appear to involve multiple cortical and subcortical areas. Controversy remains as to whether associative models or Artificial Intelligence symbolic models better reflect neural networks of cognitive functions; however, considerable interest has shifted towards associative models.

Electrocortical mapping, MRI, and neuropsychological measures: evidence of Alzheimer's disease in the presence of vascular lesions

We report here a case study of a 76-year-old woman with a high school education, whose presenting psychiatric symptomatology indicated dementia of unknown etiology. Neuropsychological test results were consistent with AD, but diagnosis was complicated by an MRI showing a large right hemisphere cortical infarct and scattered subcortical changes leading to a diagnosis of possible AD. Electrocortical mapping showed the right hemisphere infarct, and gave independent evidence suggestive of AD in the relatively intact left hemisphere. This case demonstrates the utility of multidimensional assessment as an aid to differential diagnosis.

Visual evoked potentials in dementia: selective delay of flash P2 in probable Alzheimer's disease

The flash visual evoked potential P2 component is delayed in etiologically mixed groups of demented patients compared to healthy controls or nondemented patients. This study compared patients meeting both DSM-III-R criteria for dementia and NINCDS-ADRDA criteria for probable Alzheimer's disease (AD) with healthy elderly controls and found the P2 delay in the probable AD group. Additional comparisons found no evidence of a P2 delay in demented unlikely AD patients. These results suggest that earlier findings of a delayed P2 in etiologically mixed demented groups may have been due to inclusion of AD patients.

Visual response latencies in temporal lobe structures as a function of stimulus information load

In a monkey performing a visual delayed matching-to-sample task, units and visual evoked potentials (VEPs) were sampled from the inferior bank of the superior temporal sulcus (STS; Areas TEa and IPa), the hippocampus, and the presubiculum. VEP latencies indicated that flash information--signaling the imminent presentation of a color sample to be retained--reached the presubiculum and the hippocampus substantially earlier than the STS. In contrast, color sample VEP latencies did not differ between sites, arriving at all sites appreciably later than flash VEPs. Unit data indicated generally excitatory responses to both stimuli at all sites and net inhibition during the interstimulus interval separating flash from sample. As with VEPs, unit latencies to flash were shorter than to sample stimuli. The alerting flash data imply activation of the hippocampus occurring before activation of the STS cortex, whereas the coincident arrival of color sample information suggests temporal synchronization between these structures.

Visual response latencies in temporal lobe structures as a function of stimulus information load

In a monkey performing a visual delayed matching-to-sample task, units and visual evoked potentials (VEPs) were sampled from the inferior bank of the superior temporal sulcus (STS; Areas TEa and IPa), the hippocampus, and the presubiculum. VEP latencies indicated that flash information--signaling the imminent presentation of a color sample to be retained--reached the presubiculum and the hippocampus substantially earlier than the STS. In contrast, color sample VEP latencies did not differ between sites, arriving at all sites appreciably later than flash VEPs. Unit data indicated generally excitatory responses to both stimuli at all sites and net inhibition during the interstimulus interval separating flash from sample. As with VEPs, unit latencies to flash were shorter than to sample stimuli. The alerting flash data imply activation of the hippocampus occurring before activation of the STS cortex, whereas the coincident arrival of color sample information suggests temporal synchronization between these structures.

Neuropsychological "systems efficiency" and positron emission tomography

Positron emission tomography (PET) has dramatically improved our ability to examine the functioning of the living brain. PET studies of neural pathways of the major sensory modalities--auditory, visual, somatosensory--have confirmed many traditional neuropsychological concepts, such as cross-lateral representation and regional functioning to particular primary sensory cortical areas. Other PET studies have used radioisotopes to examine relationships between radiopharmaceutical agents and neurobehavioral functioning in both normal and neuropathological states. In some areas, PET methodology requires further refinement. For example, effort should be made to develop the technology to do multiple scans within a short time frame; statistical procedures to examine relationships between neuropsychological tasks and the activity or presence of radiopharmaceutical agents in multiple sites; adequate controls for experimental error; and activation paradigms controlling the nonspecific effects of simple arousal. PET activation models of cognition suggest that a "systems efficiency" approach to assessing neuropsychological test performance involving both serial and parallel processing would be useful. These developments will improve empirical methodology and our understanding of brain-behavior relationships.

Facts and artifacts in brain electrical activity mapping

As computerized EEG (CEEG) analysis and display methods become increasingly powerful the user is lured toward increasingly abstract representations of data in which artifacts can easily go unrecognized. The presence of even small amounts of artifact can lead to distortion of CEEG results due to the sensitivity of the analysis methods employed. Several common artifacts are discussed, their distortion of CEEG data illustrated, and remedial measures suggested. Some of these artifacts (EOG, EMG, photomyoclonic, tremor, ECG, 60 Hz, volume conducted cortical activity) are familiar to traditional EEG (aliasing, extrapolation) are unique to CEEG and may be inadvertently introduced by workers not specifically trained in CEEG methods.

Potentiation of odor by taste and odor aversions in rats are regulated by cholinergic activity of dorsal hippocampus

Limbic cholinergic activity is critically involved in the retention of learned aversions tasks. The purpose of these experiments was to assess the role of cholinergic mechanisms of the dorsal hippocampus in the acquisition of both odor and potentiated odor aversions through taste aversion. Cholinergic activity was increased by physostigmine (Phys). When Phys was applied before the presentation of an odor-taste compound during acquisition, the potentiation of odor-aversion was disrupted, while taste aversion was left intact. When hippocampal cholinergic activity was reduced with the muscarinic antagonist scopolamine (Scop), enhancement of potentiated odor aversion was observed, again with no effect on taste aversion. Moreover, when Phys was applied before an odor alone it also disrupted odor avoidance in two different odor tests conditioning situations, i.e., odor was followed immediately by lithium chloride or foot shock. Neither Scop nor Phys had any effect on taste or potential odor aversions when applied to fronto-parietal cortex. These results suggest that cholinergic activity of the hippocampus is involved in the acquisition of odor aversion conditioning.

Separate channels mediate prestimulus facilitation and suppression of rabbit nictitating membrane reflex

Neurophysiological mechanisms underlying prestimulus-induced facilitation and suppression of reflex amplitude were investigated by using the rabbit nictitating membrane reflex (NMR). Experiment 1 was conducted to investigate the retractor bulbi motoneuron pool in the region of the abducens nucleus. Direct electrical stimulation of the pool caused NM extension, and recordings from the motoneurons showed greatly increased activity under conditions of NMR amplitude facilitation. Decreased motoneuron activity was conspicuously absent under conditions of NMR amplitude suppression. In Experiment 2, the retractor palpebrae tertiae motoneuron pool of the nucleus centralis caudalis was investigated. Direct electrical stimulation of the pool caused NM retraction, and recordings from the motoneurons showed increased activity under conditions of NMR amplitude suppression, but not under conditions of NMR amplitude facilitation. A quantitative model constructed from these neurophysiological results was shown to generate predictions in close accord with directly measured NMR amplitudes under both suppressive and facilitative conditions. From these results it appears that the behaviorally independent processes of NMR amplitude facilitation and suppression are mediated by anatomically independent motoneuron pools and output pathways showing no evidence of central inhibition but opposing each other peripherally through simultaneous excitation of antagonistic muscles.

Separate channels mediate prestimulus facilitation and suppression of rabbit nictitating membrane reflex

Neurophysiological mechanisms underlying prestimulus-induced facilitation and suppression of reflex amplitude were investigated by using the rabbit nictitating membrane reflex (NMR). Experiment 1 was conducted to investigate the retractor bulbi motoneuron pool in the region of the abducens nucleus. Direct electrical stimulation of the pool caused NM extension, and recordings from the motoneurons showed greatly increased activity under conditions of NMR amplitude facilitation. Decreased motoneuron activity was conspicuously absent under conditions of NMR amplitude suppression. In Experiment 2, the retractor palpebrae tertiae motoneuron pool of the nucleus centralis caudalis was investigated. Direct electrical stimulation of the pool caused NM retraction, and recordings from the motoneurons showed increased activity under conditions of NMR amplitude suppression, but not under conditions of NMR amplitude facilitation. A quantitative model constructed from these neurophysiological results was shown to generate predictions in close accord with directly measured NMR amplitudes under both suppressive and facilitative conditions. From these results it appears that the behaviorally independent processes of NMR amplitude facilitation and suppression are mediated by anatomically independent motoneuron pools and output pathways showing no evidence of central inhibition but opposing each other peripherally through simultaneous excitation of antagonistic muscles.

The elgiloy microelectrode: fabrication techniques and characteristics

A glass-insulated microelectrode made from elgiloy orthodontic wire, a stainless cobalt-chromium alloy containing 15% iron, was described by Suzuki and Azuma (1976). Here, we detail a set of modified electrode fabrication procedures, including techniques for hardening and etching the wire, specifying the size, geometry and exposure of the tip, and adjusting tip impedance over a wide range. Accurate insulation of the tip with molten solder glass produces microelectrodes suitable for extracellular recording from single or multiple units and simultaneous recording of evoked potentials. The finished electrode is tough enough to withstand multiple penetrations of the thickened, fibrous dura of the chronic monkey preparation. The iron content allows Prussian blue staining of marking lesions for histological verification of recording sites.

Taste potentiation of poisoned odor by temporal contiguity

The synergistic interaction between odor and taste in flavor-toxicosis conditioning was tested in two experiments. The temporal interval between a 2-min odor and a 2-min taste was varied for thirsty rats licking at a water spout. In the first experiment, taste was presented at time zero, and odor was presented at -10, -1, 0, 1 and 10 min to independent groups in a simple compartment. In the second experiment, taste was presented at 0, and odor was presented at -5, -2, and 0 min in a "wind tunnel" apparatus. The results indicated that odor alone is an ineffective conditioned stimulus for a toxic unconditioned stimulus under our conditions, simultaneous (0-min) presentation of odor with taste potentiates the odor component so that it becomes more effective than the taste component, a 2-min interval between odor and taste attenuates potentiation, and a 5-min interval disrupts the effect, and the interaction in asymmetrical, that is, odor has no such systematic effect on the conditioning of taste.

Taste potentiation of poisoned odor by temporal contiguity

The synergistic interaction between odor and taste in flavor-toxicosis conditioning was tested in two experiments. The temporal interval between a 2-min odor and a 2-min taste was varied for thirsty rats licking at a water spout. In the first experiment, taste was presented at time zero, and odor was presented at -10, -1, 0, 1 and 10 min to independent groups in a simple compartment. In the second experiment, taste was presented at 0, and odor was presented at -5, -2, and 0 min in a "wind tunnel" apparatus. The results indicated that odor alone is an ineffective conditioned stimulus for a toxic unconditioned stimulus under our conditions, simultaneous (0-min) presentation of odor with taste potentiates the odor component so that it becomes more effective than the taste component, a 2-min interval between odor and taste attenuates potentiation, and a 5-min interval disrupts the effect, and the interaction in asymmetrical, that is, odor has no such systematic effect on the conditioning of taste.