In our recent work with infants born full-term, 31 we showed that infants born full-term learned the association between kicking and mobile movement. Specifically, they increased their kicking rate as compared with their own baseline kicking rate and with a comparison group who saw a moving mobile but whose tethered leg did not cause mobile movement.
The infants born full-term showed an increased kicking rate within one session learning period and retained an elevated rate for 24 hours short-term memory period and for 1 week long-term memory period. Because only the right leg was tethered to the mobile, the task required only that infants kick the right leg to move the mobile.
The first purpose of the present study was to determine how infants adapt the baseline kicking frequencies of both legs to meet task demands. Given that the infants born full-term rapidly learned the associative learning aspect of the paradigm and that they displayed the ability to dissociate their legs during spontaneous kicking, we hypothesized that infants born full-term would preferentially increase the kicking frequency of the tethered leg during the learning period and maintain this pattern during both the short-term and long-term memory periods.
Several studies have examined the spontaneous kicking of infants born preterm; however, very few studies have examined their kicking in a task-specific manner such as within the mobile paradigm.
Thus, the second purpose of the present study was to determine whether this increase in tethered kicking frequency was specific to the tethered leg, as predicted for the infants born full-term, or was simply a general increase in the kicking frequency of both legs.
Given that these infants born preterm 31 displayed neither associative learning in the mobile paradigm nor the typical ability to dissociate their leg kicks during spontaneous kicking, we hypothesized that they would not preferentially increase the kicking frequency of the tethered leg during the learning period but would equally increase the kicking frequency of both legs.
Moreover, we hypothesized that they would maintain a relatively equal kicking frequency with both legs during the short-term and long-term memory periods, similar to the comparison group. A total of 30 infants aged 3 to 4 months participated in the study. Infants were excluded from participation for any known visual or orthopedic diagnosis. Ten infants were in each of 3 groups: full-term, comparison, and preterm Tab.
As reported earlier, the initial visit, the infants' ages, and gross motor skills did not differ. Detailed information on selection criteria, group assignment, and the infants' characteristics is provided in our previous report.
Table 3 shows the available medical history and follow-up information from 8 of the 10 infants born preterm. The infants born preterm spent an average of Four of the 8 infants did not have imaging tests at birth, 1 infant was diagnosed with periventricular leukomalacia, and 2 infants were diagnosed with intraventricular hemorrhage.
Data not available for infants 7 and 8. Two identical white plastic mobile stands were attached to the right and left sides of the infants' home cribs Fig. A white ribbon and a small, soft cuff were used to tether each infant's right leg to the right stand. Testing sessions were completed in the infants in their home cribs. Each infant was placed in a supine position by a parent who then remained out of the infant's sight.
For the comparison group, the mobile remained on the left stand while an investigator, who remained out of the infants' view, used a transparent wire to move the mobile. Infants in the full-term and comparison groups were seen for 3 sessions, on 2 consecutive days and then 1 week later.
Using a normalized kicking frequency, the infants in the full-term group displayed learning on day 1, short-term memory 24 hours later on day 2, and long-term memory 1 week later on day 3. The comparison group did not increase their kicking during learning or memory period.
Infants in the preterm group were seen for 2 consecutive days each week for 6 weeks. The infants in the preterm group, however, did show an increase in kicking during certain acquisition or extinction period as compared with their own baseline for that day.
Therefore, relative kicking frequency was analyzed during the time period when this increase was observed. A kick was defined as a simultaneous extension of the hip and knee with immediate recoil of flexion. Tethered leg right and nontethered leg left kicks were counted during all time periods of each session.
Intrarater and interrater reliability for kicking frequency were. To test whether infants kicked differently during acquisition and extinction as compared with baseline, relative kicking frequency scores were compared within each group by separate repeated-measures analyses of variance ANOVAs across time periods of the same day, followed with planned comparisons between periods. To test whether infants retained the same or different kicking patterns in later sessions as they displayed during learning, relative kicking frequency scores were compared within each group by separate repeated-measures ANOVAs across the baseline periods of 2 days separated by 24 hours for short-term memory and across baseline periods separated by 1 week for long-term memory.
The relative kicking frequencies for these baseline periods also were compared between the full-term and comparison groups and between the preterm and comparison groups with separate independent t tests. Infants born full-term showed an increase in the relative kicking frequency of the tethered leg over one minute session.
The relative kicking frequency Fig. The standard deviations were high, ranging from 4. Relative kicking frequency of full-term and comparison group infants across all sessions.
During baseline day 1, the infants born full-term had a mean of 6. Within the first 3 minutes of acquisition day 1, infants born full-term began kicking their tethered leg. For the comparison group, the relative kicking frequency Fig. The standard deviations were high, varying from 6.
The full-term group proportionally increased their relative kicking frequency such that the tethered leg kicked more frequently as soon as kicking led to mobile movement acquisition 01 , whereas the comparison group, whose leg kicks did not cause mobile movement, did not show this change.
The full-term group also showed a difference in the relative kicking frequency compared with the comparison group. In addition to group differences, individual infants in the full-term and comparison groups differed. Eight of the 10 infants in the full-term group increased the relative kicking frequency during extinction compared with baseline. In contrast, only 3 of the 10 infants in the comparison group showed an increase Fig.
Relative kicking frequency of individual infants in the full-term and comparison groups during day 1 learning. In contrast to infants born full-term, infants born preterm did not show an increase in relative kicking frequency at any point during the 6 weeks of testing.
As reported previously, 31 infants in the preterm group had increased the normalized kicking frequencies of their tethered leg in comparison with their own baseline level on week 1 day 1, week 2 day 1, and week 4 day 1. Thus, the relative kicking frequency was statistically analyzed during these periods. During baseline day 1, the preterm group's relative kicking frequency was Relative kicking frequency of preterm group infants across all sessions. Five of the 10 infants born preterm showed an increase in relative kicking frequency during extinction as compared with baseline on day 1.
Planned comparisons between baseline and acquisition 01, acquisition 02, and acquisition 03 for week 2 day 1 and week 4 day 1 were not significant. Additionally, there were no differences in relative kicking frequency between the preterm group and the comparison group. On an individual level, 4 to 6 infants born preterm showed an increase in relative kicking frequency from baseline to extinction during any given week.
Infants in the full-term group maintained an increase in relative kicking frequency for the short-term memory period 24 hours later , but not for the long-term memory period 1 week later. We continued with this analysis as the comparisons between the relative kicking frequency between baseline day 1 and day 2 short-term memory and the relative kicking frequency between baseline day 1 and day 3 long-term memory were planned.
Full-term and comparison groups differed at the level of individual infants. Eight of the 10 full-term group infants increased their relative kicking frequency during baseline day 2 compared with baseline day 1.
In contrast, only 1 of the 10 infants in the comparison group showed an increase Fig. Although the groups did not differ during the long-term memory period, 6 of the 10 infants born full-term increased their relative kicking frequency during the long-term memory period, whereas no infants from the comparison group showed an increase.
Relative kicking frequency of individual infants in the full-term and comparison groups during day 2 short-term memory. The preterm group did not display short-term and long-term memory over the 6 weeks of testing. Their kicking did not differ between the baseline periods between any 2 weeks of testing.
On an individual level, 4 to 6 infants born preterm showed an increase in the relative kicking frequency from baseline day 1 to baseline of any other weeks. Our hypotheses regarding the relative kicking frequencies of the full-term group and the preterm group during the learning and memory periods in the mobile paradigm were supported with one exception. As predicted, infants born full-term were able to independently learn a task-specific pattern of kicking within the first minute session and retain that pattern for 24 hours.
Unexpectedly, infants born full-term did not retain this pattern for 1 week. Also as expected, infants born preterm displayed a relatively equal kicking frequency of their tethered and nontethered legs during all 12 sessions across the 6 weeks. Our results extend those of a previous study in which infants born full-term increased movement in whichever limb was tethered to the mobile during a single session.
Second, our results suggest that these infants can retain this task-specific pattern for 24 hours following the initial learning period. Although these infants displayed long-term memory for the initial associative learning, as evidenced by an increase in tethered leg kicks, 31 they also increased nontethered leg kicks so that tethered and nontethered leg kicks were not statistically different than the pre-exposure relative kicking frequency.
Taken together, our results suggest that, although infants born full-term retained the memory for the association between leg movement and mobile movement for up to 1 week, they retained the task-specific relative kicking frequency only for 24 hours. In contrast, the preterm group displayed relative kicking frequencies after exposure to the mobile reinforcement that were not different from their baseline pattern on day 1 before any exposure to the mobile.
Their relative kicking frequencies also did not differ from those of the infants in the comparison group. That is, the increase in tethered leg kicks by these infants 31 was accompanied by an equal increase in kicking frequency of the nontethered leg Fig. This lack of a task-specific pattern was also noted at the level of individual infants in that equivalent numbers of infants born preterm showed a task-specific pattern and an equal kicking frequency between legs during each day of testing.
Developmental changes in motor behaviors have been proposed to emerge out of the social, cognitive, and perceptual-motor aspects of past experiences as well as the current context and task requirements. This suggests the potential for a relationship between spontaneous kicking patterns and those patterns used as infants perform in the mobile paradigm.
Specifically, newborn infants born full-term kick with a stereotypically alternating pattern, which becomes more variable and includes frequent individual leg kicks over the next 6 months.
In contrast, infants born preterm spontaneously kick with a higher interlimb correlation and display fewer interlimb kick patterns than infants born full-term. Infants born preterm differed from infants born full-term in their ability to produce task-specific leg movements during a task in which leg movements were directly associated with mobile movement.
This suggests a potentially important connection between associative learning and neuromotor control during early infancy. That is, the inability of these infants to disassociate their leg movements may have affected their ability to learn the basic association between leg movement and mobile movement. Alternatively, if these infants were unable to rapidly learn the association between leg and mobile movement, then mobile movement may have caused an increase in kicking simply via arousal.
That is, it is possible that infants born preterm may not have shown a task-specific kicking pattern because they may not have realized that the mobile could be manipulated via kicking.
Colic usually begins by 2 to 3 weeks of age and lasts up to 3 or 4 months of age. The crying may or may not occur at the same time each day, but usually happens more often in the evening.
The baby does not stop crying when usual ways of comforting, such as holding and feeding, are tried. The colicky infant usually shows these signs:. No one knows the real cause of colic, but some things that may be related include:. There is no sure treatment for colic, so it may be difficult to comfort your crying baby.
The following suggestions have been tried by other parents who have had colicky infants:. Call your child's doctor if your baby has any of these symptoms:. Colic is a common concern. It affects 1 in 4 infants and can cause the entire family a great deal of distress.
Usually colic will end between the infant's third and sixth months of life. A baby who cries too much despite everything you do to comfort him can make the parents nervous and angry. It is important for you to remember the following things:. Remember, it is okay to walk away if you find yourself getting frustrated or angry with your baby or child. Your baby will not be hurt if he or she continues to cry. Gently and safely place your baby in the crib or swing.
Make sure you secure any railings or safety belts before walking away. Check on your baby every 5 to 10 minutes. Skip to Content. Urgent Care. In This Section. You can help your child by providing a safe place to practice moving and lots of interesting objects to reach for or move toward. By now babies can hold their head and chest up when lying on their stomach.
They begin lifting their head and chest further by straightening the arms and using chest and back muscles. Your child also might begin moving his or her legs and rocking on the stomach. In this way, babies are getting ready to roll over and build up to crawling.
During this period, your baby will probably learn to roll over in both directions. So be sure to never leave your little one unattended. These newfound movements could cause a child to fall from a bed or couch unless supervised. Even if your child never rolled over before, there's always a first time. Babies like to surprise parents that way. With improved neck and trunk strength, babies can start to sit when placed in that position with support.
Your baby will learn to lean forward with arms stretched out for support. Your baby will gain the strength and confidence to sit unaided over time, but will still need some help to get into a sitting position. Legs are also getting stronger.
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