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PubMed2000

Mental maze solving.

We sought to determine how a visual maze is mentally solved. Human subjects (N = 13) viewed mazes with orthogonal, unbranched paths; each subject solved 200-600 mazes in any specific experiment below. There were four to six openings at the perimeter of the maze, of which four were labeled: one was the entry point and the remainder were potential exits marked by Arabic numerals. Starting at the entry point, in some mazes the path exited, whereas in others it terminated within the maze. Subjects were required to type the number corresponding to the true exit (if the path exited) or type zero (if the path did not exit). In all cases, the only required hand movement was a key press, and thus the hand never physically traveled through the maze. Response times (RT) were recorded and analyzed using a multiple linear regression model. RT increased as a function of key parameters of the maze, namely the length of the main path, the number of turns in the path, the direct distance from entry to termination, and the presence of an exit. The dependence of RT on the number of turns was present even when the path length was fixed in a separate experiment (N = 10 subjects). In a different experiment, subjects solved large and small mazes (N = 3 subjects). The former was the same as the latter but was scaled up by 1.77 times. Thus both kinds of mazes contained the same number of squares but each square subtended 1.77 degrees of visual angle (DVA) in the large maze, as compared to 1 DVA in the small one. We found that the average RT was practically the same in both cases. A multiple regression analysis revealed that the processing coefficients related to maze distance (i.e., path length and direct distance) were reduced by approximately one-half when solving large mazes, as compared to solving small mazes. This means that the efficiency in processing distance-related information almost doubled for scaled-up mazes. In contrast, the processing coefficients for number of turns and exit status were practically the same in the two cases. Finally, the eye movements of three subjects were recorded during maze solution. They consisted of sequences of saccades and fixations. The number of fixations in a trial increased as a linear function of the path length and number of turns. With respect to the fixations themselves, eyes tended to fixate on the main path and to follow it along its course, such that fixations occurring later in time were positioned at progressively longer distances from the entry point. Furthermore, the time the eyes spent at each fixation point increased as a linear function of the length and number of turns in the path segment between the current and the upcoming fixation points. These findings suggest that the maze segment from the current fixation spot to the next is being processed during the fixation time (FT), and that a significant aspect of this processing relates to the length and turns in that segment. We interpreted these relations to mean that the maze was mentally traversed. We then estimated the distance and endpoint of the path mentally traversed within a specific FT; we also hypothesized that the next portion of the main path would be traversed during the ensuing FT, and so on for the whole path. A prediction of this hypothesis is that the upcoming saccade would land the eyes at or near the locus on the path where the mental traversing ended, so that "the eyes would pick up where the mental traversal left off." In this way, a portion of the path would be traversed during a fixation and successive such portions would be strung together closely along the main path to complete the processing of the whole path. We tested this prediction by analyzing the relations between the path distance of mental traverse and the distance along the path between the current and the next fixation spot. (ABSTRACT TRUNCATED)

Adult↗
PubMed1996

Maze learning by honeybees.

This study examines whether honeybees can learn to fly through complex mazes, in the presence or the absence of specific visual cues. The results are summarized as follows: 1. Bees can learn to fly through a complex maze by following a trail of colored marks. 2. Bees, initially trained to follow color marks through an initial part of the maze, are immediately able to use the same sign-tracking cue to find their way through the rest of the maze, which is unfamiliar to them. 3. Bees trained to follow color marks through a particular maze can use the same cue to negotiate a novel maze. 4. Bees trained to use a particular color to negotiate a maze can immediately use a novel color to negotiate the same maze or even a novel maze. 5. After learning to negotiate a maze by following colored marks, bees can find their way through the maze even when the marks are removed, albeit at reduced levels of accuracy. Thus, the trained bees do not rely solely on sign-tracking to find their way through the maze: they also acquire a spatial memory of the maze or at least a sequence of motor commands describing the correct path through it. 6. Bees can learn to use color as a signal even when it indicates the path through the maze in a symbolic way, for example, blue indicating a turn to the right and green a turn to the left. 7. Bees can learn an unmarked maze. Performance under these conditions is poorer than when marks are provided, but is still significantly better than chance level. 8. Control experiments rule out the use of external landmarks in all of these situations.

Animals↗
PubMed2004

Comparison of the role of somatosensory stimuli in maze learning in a blind subterranean rodent and a sighted surface-dwelling rodent.

We compared the role of tactile perception in maze learning in the blind mole rat and in the laboratory rat. Both species were tested in each of two mazes that were identical in complexity but differed in tunnel width and height: the first was only slightly wider than the animal's body width (narrow maze) while the second was about twice the animal's body width (wide maze). We found that the performances of rats tested in the narrow maze were significantly lower than those tested in the wide maze, as measured by time and number of errors to reach the end of the maze (food reward). The mole rats, in contrast, performed significantly better in the narrow maze than in the wide maze. Further, in contrast to the rats, the mole rats' locomotion in the wide maze was much less continuous than in the narrow maze, reflected in longer and more frequent stops at maze junctions, where they pressed the side of their body tightly against the tunnel walls. Two main conclusions are derived from this experiment. First, subterranean mammals, such as the blind mole rat, appear to rely more on tactile stimuli while exploring and learning a complex maze than do sighted surface-dwelling rodents, such as rat. The extensive use of this somatosensory channel may compensate for the mole rats' visual deficiency, and thus substantially contribute to their excellent spatial orientation ability, previously demonstrated in field and laboratory conditions. Second, poor performance of surface-dwelling rodents, such as the rats, in spatial-maze learning tasks might not be a consequence of impaired cognitive learning ability, but rather due to testing the animal in a physical situation that does not provide the necessary somatosensory stimuli found in their natural habitat.

Animals↗
PubMed1991

Effects of MK-801 on learning and memory as assessed using a novel water maze.

The effects of the NMDA receptor antagonist MK-801 [(+)-10,11-dihydro-5-methyl-5H-dibenzo [a,d]-cyclohepten-5,10 imine hydrogen maleate] on learning and memory were assessed using a water maze. The maze was a traditional type of maze with alleys and choices between various paths, but set inside a pool of water to a height of 25 cm. Different mazes could be configured by altering the arrangement of open vs. closed doors. Both the time required to reach an out-of-the-water exit platform and the errors made during the swim from start to finish were recorded. Learning was assessed during the first 10 to 20 trials in a new maze configuration, while memory was tested after the maze was well learned. Three experiments, some with several phases, were performed. These experiments compared the effects of 0.1 mg/kg of either (+)-MK-801, or (-)-MK-801 vs. saline on learning new maze configurations as well as swimming well-learned mazes. Neither of the MK-801 isomers impaired performance of a previously learned maze. (+)-MK-801 clearly slowed learning of new mazes as measured by both maze completion time and errors committed, while (-)-MK-801 had a significant but smaller effect on learning. Rats given (+)- or (-)-MK-801 (0.1 mg/kg) for 16 days while learning one maze and then challenged to learn a new maze without drug administration performed no differently on the new maze than controls, suggesting that the acute effect of MK-801 on learning is not long lasting.

Animals↗
PubMedDate not supplied

Maze navigation by honeybees: learning path regularity.

We investigated the ability of honeybees to learn mazes of four types: constant-turn mazes, in which the appropriate turn is always in the same direction in each decision chamber; zig-zag mazes, in which the appropriate turn is alternately left and right in successive decision chambers; irregular mazes, in which there is no readily apparent pattern to the turns; and variable irregular mazes, in which the bees were trained to learn several irregular mazes simultaneously. The bees were able to learn to navigate all four types of maze. Performance was best in the constant-turn mazes, somewhat poorer in the zig-zag mazes, poorer still in the irregular mazes, and poorest in the variable irregular mazes. These results demonstrate that bees do not navigate such mazes simply by memorizing the entire sequence of appropriate turns. Rather, performance in the various configurations depends on the existence of regularity in the structure of the maze and on the ease with which this regularity is recognized and learned.

Animals↗
PubMed2006

The impact of mitral valve surgery combined with maze procedure.

OBJECTIVE: Recent studies indicated that successful maze procedure for atrial fibrillation (AF) adjunct to mitral valve surgery provided a lower incidence of stroke and recurrence of AF. The purpose of this study is to review the 13-year experience of these combined procedures and to identify the risk factors and late outcomes of successful maze procedures compared to failed maze procedures. METHODS: At a single institution, 521 consecutive patients underwent combined maze procedures with mitral valve replacements or valvuloplasties. Three kinds of maze techniques were primarily used: Cox-maze III, Kosakai maze, and cryo-maze procedure. Three months after the operation, 394 patients were in sinus rhythm (Group S) while the remaining 116 patients were in continuous or intermittent AF (Group F), excluding 11 early death patients. Risk factors for Group F were determined by the analysis of all patient demographics. Survival, freedom from stroke, cardiac events, and AF recurrence were analyzed. RESULTS: The proportion of the patients without any other simultaneous procedures was greater in Group S (41% vs 29%, P = 0.02). The distributions of mitral valve surgery and maze procedure techniques were similar in these two groups. A left atrium larger than 70 mm [hazard ratio (HR) = 2.6; 95% confidence interval range 1.04-6.3, P = 0.043], preoperative AF history longer than 10 years (HR = 8.2; 4.5-15.1, P < 0.001) and f-wave voltage in V1 smaller than 0.1 mV (HR = 6.2; 5.0-15.2, P < 0.001) were determined to be risk factors for unsuccessful maze procedures. All the results of Cox proportional hazards models showed superiority in Group S; actuarial survival rates (HR = 2.7; 1.04-7.0, P = 0.035), freedoms from stroke (HR = 3.0; 1.1-8.1, P = 0.003) and cardiac events (HR = 4.3; 2.9-6.1, P < 0.001). Freedom from AF recurrence rate was 98.4% at 5 years and 81.0% at 12 years in Group S, and 73.0% and 60.1% in overall patients. CONCLUSIONS: Patients with successful maze procedures resulted in higher survival rate, greater freedom from stroke and cardiac events. The large left atrium, small f-wave, and long AF duration were significant risk factors for failed maze procedures, suggesting that earlier surgical interventions would result in superior results in mitral valve surgery combined with maze procedure.

Adult↗
PubMed1998

Effect of the Cox maze procedure on the secretion of atrial natriuretic peptide.

OBJECTIVES: The Cox maze procedure has been confirmed to be effective in curing atrial fibrillation. Some authors have reported severe fluid retention after the Cox maze procedure and have suggested decreased secretion of atrial natriuretic peptide as a possible mechanism. This study was designed (1) to examine the serial changes in atrial natriuretic peptide after the Cox maze procedure as compared with changes occurring after coronary artery bypass grafting and (2) to elucidate any differences in atrial natriuretic peptide levels between patients with transient recurrence of atrial fibrillation after the Cox maze procedure and those without recurrence of atrial fibrillation. METHODS: Blood samples were drawn from the right and left atria in patients undergoing the Cox maze procedure (n = 19) and from the right atrium in patients undergoing coronary artery bypass grafting (n = 6) before and 1, 2, and 3 days after the operation. In six patients undergoing the Cox maze procedure, samples were also drawn from the radial artery before and 1, 2, 3, 5, and 7 days after the operation. The plasma samples were prepared by refrigerated centrifugation and stored until radioimmunoassay. In the Cox maze procedure group, atrial natriuretic peptide levels in the right atrium were 629 +/- 366, 154 +/- 112, 162 +/- 112, and 183 +/- 97 pg/ml and those in the left atrium were 276 +/- 168, 152 +/- 91, 162 +/- 111, and 145 +/- 80 pg/ml before and 1, 2, and 3 days after the operation, respectively. A marked decrease in atrial natriuretic peptide levels was evident after the Cox maze procedure (p < 0.001). There was no significant correlation between atrial natriuretic peptide levels and atrial pressures after the Cox maze procedure, which suggests that secretion of atrial natriuretic peptide by the atria was impaired. There was a significant correlation between the atrial natriuretic peptide levels in the left atrium and those in the peripheral radial artery, and the decreased levels of atrial natriuretic peptide in the radial artery continued for 7 days after the Cox maze procedure. There were no differences in the atrial natriuretic peptide levels between the patients with transient recurrence of atrial fibrillation (n = 6) and those without recurrence (n = 13) after the Cox maze procedure. In the coronary artery bypass grafting group, the atrial natriuretic peptide levels in the right atrium were 115 +/- 37, 124 +/- 48, 154 +/- 54, and 156 +/- 36 pg/ml before and 1, 2, and 3 days after the operation, respectively. No change was seen after the operation. CONCLUSIONS: We observed a significant decrease in atrial natriuretic peptide levels after the Cox maze procedure. This may be one of the possible causes of fluid retention after this procedure. These decreased atrial natriuretic peptide levels after the Cox maze procedure may result from the multiple atriotomy incisions and excision of both atrial auricles performed during the procedure, rather than from the conversion of atrial fibrillation to normal sinus rhythm.

Atrial Fibrillation↗
PubMed2000

T-maze behaviour in broiler chicks is not sensitive to right-left preferences, test order or time-of-day.

There is substantial individual variation in the time taken by broiler chicks to traverse a T-maze and thereby reinstate visual contact with their companions. Chicks completing this task quickly (high performance, HP) subsequently grew faster in the laboratory and on farm, exhibited greater sociality, and showed less pronounced adrenocortical responses to a partial water immersion stressor than did their slower (low performance, LP) counterparts [Marin, R.H., Jones, R.B., 1999. Latency to traverse a T-maze at 2 days of age and later adrenocortical responses to an acute stressor in domestic chicks. Physiol. Behav. 66, 809-813.; Marin, R.H., Arce, A., Martijena, I.D., 1997. T-maze performance and body weight relationship in broiler chicks. Appl. Anim. Behav. Sci. 54, 197-205.; Jones, R.B., Marín, R.H., García, D.A., Arce, A., 1999. T-maze behaviour in domestic chicks: a search for underlying variables. Anim. Behav. 58, 211-217.]. Given its simplicity, rapidity and non-invasiveness, the T-maze test might represent a commercially attractive selection criterion for future breeding programmes if this behavioural trait exhibits sufficient genetic variability. However, it is first necessary to ensure that performance in the T-maze is not sensitive to potentially confounding variables, such as existing preferences to turn right or left at the junction of the maze, the order of testing, or the time of day. In the present study, 240 newly hatched, mixed-sex broiler chicks (Cobb) were randomly allocated to 12 groups of 20 upon receipt. When they were 2 days of age a group of 20 chicks was placed in the brood area of each of two T-mazes at 0830 h; the brood areas were positioned on either the right or the left sides of the mazes. After acclimatisation, one chick from each group was placed in the isolation chamber of the T-maze and we recorded the time it took to traverse the maze. This procedure was repeated until all 20 chicks and all 12 groups had been tested. The locations of the brood areas were rotated after each block of 20 tests. Testing was completed in the same day and two groups were tested at each of the following times: 0900, 1030, 1200, 1330. 1500, and 1630 h. Analyses of variance (ANOVA) revealed no detectable effects of: positioning the brood area on the right or the left side of the T-maze (F(1,200)=0.06, P<0.80), test order (F(19,200)=0.48; P<0.96), or time-of-day (F(5,234)=0.44; P<0.81). These findings strongly suggest that the future classification and possible selection of broiler chicks according to their T-maze responses are unlikely to be confounded by right-left preferences, test order, or the time of day.

Journal Article↗
PubMed1997

Electrophysiologic changes in arrhythmogenic substrate following the maze procedure in patients with lone and paroxysmal atrial fibrillation.

Although the Maze procedure is highly successful in restoring sinus rhythm in patients with atrial fibrillation (AF), the electrophysiologic changes that occur after the Maze procedure and its mechanism of action are still unclear. The aims of the present study were to examine the electrophysiologic changes that occur in the arrhythmogenic substrate after the Maze procedure and to evaluate the mechanism by which it prevents lone and paroxysmal AF. The modified Maze procedure was performed in 6 patients (6 men, mean age 47 +/- 7 years) with lone and paroxysmal AF. Electrophysiologic studies were performed before and 35 +/- 8 days after the Maze procedure. Atrial mapping during sinus rhythm revealed that atrial activation propagated smoothly in a concentric circle from the sinus node to other regions in the right atrium and into the coronary sinus before the Maze procedure. Following the Maze procedure, atrial activation propagated selectively through routes produced by incisions or cryoablations in all 6 patients. In addition, double and triple potentials were recorded in regions where conduction blocks were created by the Maze procedure. Neither sinus node function nor AV conduction was changed following the Maze procedure. The Maze procedure did not affect the atrial effective refractory period or the zone of fragmented atrial activity, although the conduction delay zone was increased significantly (p < 0.05). AF was inducible in all 6 patients before the Maze procedure, whereas it was not inducible in any patients after the Maze procedure. The Maze procedure is effective in preventing AF without affecting sinus node function and AV conduction. Intra-atrial conduction block produced by incisions or cryoablations contributes to the prevention of AF.

Adult↗
PubMed1998

Maze procedure for atrial fibrillation associated with atrial septal defect.

BACKGROUND: Atrial fibrillation (AF) is a relatively common complication in elderly patients with an atrial septal defect (ASD). However, use of the simultaneous maze procedure for AF associated with ASD remains controversial. We examined the efficacy and risk of the use of the maze procedure in these patients. METHODS AND RESULTS: Between March 1992 and April 1997, 26 patients underwent the maze procedure as a concomitant operation with ASD closure (maze group). Kosakai's modified maze procedure was performed in 17 patients, the modified Cox maze II or III procedure was performed in 6, and the restrictive right-sided maze procedure was performed in 3. The mean +/- SD age at surgery was 58.2 +/- 9.1 years. The mean +/- SD duration of AF was 7.8 +/- 8.5 years. The mean +/- SD left atrial dimension was 47 +/- 9 mm, and 24 patients (92%) had a larger-than-normal (> 35 mm) left atrium. The mean +/- SD follow-up period was 2.7 +/- 1.7 years. There were no hospital or late deaths. There was no thromboembolic episode in the late follow-up period. Sinus rhythm was regained in all patients who underwent conventional the right- and left-sided maze procedure except for 1 patient. However, 3 patients who underwent the restrictive right-sided maze procedure showed a return to AF rhythm. The atrial A wave was detected with the use of pulsed Doppler study in all patients who had a restored sinus rhythm. During the same period, 45 patients who were > 40 years old and without AF underwent only ASD closure (control group). The incidence of reopening the chest for bleeding was significantly (P = 0.046) higher in the maze group (12%) than in the control group (0%). Paroxysmal AF more frequently (P = 0.023) occurred in the control group (18%) than in the maze group (0%). CONCLUSIONS: These results suggest that the standard maze procedure should be considered in patients with AF associated with ASD. The restrictive right-sided maze procedure was not reliable, probably due to preoperative enlargement of the left atrium.

Aged↗