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Updated: Apr 27, 2026
Use of an Eight-arm Radial Water Maze to Assess Working and Reference Memory Following Neonatal Brain Injury
Published on: December 4, 2013
Spatial working memory deficits in male rats following neonatal hypoxic ischemic brain injury can be attenuated by
Amanda L Smith1, Courtney A Hill2, Michelle Alexander3
1Behavioral Neuroscience Division, Department of Psychology, University of Connecticut, 406 Babbidge Road, Unit 1020, Storrs, CT 06269, USA. amanda.l.smith@uconn.edu.
Insights
Hypoxia-ischemia (HI) in infant rats impairs working memory, especially when tasks are difficult from the start. Gradual task introduction aids learning, but impulsivity persists, mirroring ADHD symptoms in human infants.
Area of Science:
- Neuroscience
- Developmental Biology
- Pediatrics
Background:
- Hypoxia-ischemia (HI) is a common neonatal complication affecting premature and full-term infants.
- HI can cause significant brain injury, leading to long-term cognitive and behavioral deficits, particularly in working memory.
- Working memory impairments are linked to increased developmental disorders and ADHD symptoms.
Purpose of the Study:
- To investigate the impact of neonatal HI on working memory in a rodent model.
- To assess how task difficulty and learning format influence working memory performance in HI-affected rats.
- To characterize behavioral impulsivity as a potential symptom of HI-induced cognitive deficits.
Main Methods:
- Neonatal HI was induced in P7 rat pups, an age comparable to term-born human infants.
- An eight-arm radial water maze was used to assess spatial working memory.
- Two studies varied task difficulty presentation (gradual vs. immediate) and trial frequency to evaluate learning and performance.
Main Results:
- Rats exposed to HI showed a significant working memory deficit when the task presented high initial difficulty and limited trials.
- A graded, multi-trial approach allowed HI rats to learn the complex spatial task, though deficits were still observed under delayed conditions.
- HI rats consistently exhibited impulsive behavior, characterized by reduced choice latencies and increased errors, consistent with ADHD symptoms.
Conclusions:
- Task-specific modifications, such as gradual introduction of difficulty, are crucial for assessing and potentially accommodating working memory deficits in HI survivors.
- Neonatal HI can lead to persistent impulsivity, a behavioral phenotype relevant to ADHD in affected children.
- Rodent models provide valuable insights into the cognitive and behavioral consequences of neonatal HI, informing potential therapeutic strategies.
Abstract:
Hypoxia-ischemia (HI; reduction in blood/oxygen supply) is common in infants with serious birth complications, such as prolonged labor and cord prolapse, as well as in infants born prematurely (<37 weeks gestational age; GA). Most often, HI can lead to brain injury in the form of cortical and subcortical damage, as well as later cognitive/behavioral deficits. A common domain of impairment is working memory, which can be associated with heightened incidence of developmental disorders. To further characterize these clinical issues, the current investigation describes data from a rodent model of HI induced on postnatal (P)7, an age comparable to a term (GA 36-38) human. Specifically, we sought to assess working memory using an eight-arm radial water maze paradigm. Study 1 used a modified version of the paradigm, which requires a step-wise change in spatial memory via progressively more difficult tasks, as well as multiple daily trials for extra learning opportunity. Results were surprising and revealed a small HI deficit only for the final and most difficult condition, when a delay before test trial was introduced. Study 2 again used the modified radial arm maze, but presented the most difficult condition from the start, and only one daily test trial. Here, results were expected and revealed a robust and consistent HI deficit across all weeks. Combined results indicate that male HI rats can learn a difficult spatial working memory task if it is presented in a graded multi-trial format, but performance is poor and does not appear to remediate if the task is presented with high initial memory demand. Male HI rats in both studies displayed impulsive characteristics throughout testing evidenced as reduced choice latencies despite more errors. This aspect of behavioral results is consistent with impulsiveness as a core symptom of ADHD-a diagnosis common in children with HI insult. Overall findings suggest that task specific behavioral modifications are crucial to accommodating memory deficits in children suffering from cognitive impairments following neonatal HI.
